This week is now over the halfway point of the Champions League group stage, and matchday four has plenty of big games -- and big implications -- to cover. You may have seen these fixtures before in matchday three, but it's now the reverse as the away side is at home this time around.

Manchester United won't want a repeat of their embarrassing defeat to Istanbul Basaksehir, while PSG will be looking to peg back RB Leipzig's lead in second place of Group H. Elsewhere in the groups, Liverpool now host Atalanta, while Barcelona, Bayern Munich and Real Madrid will be looking to put disappointing weekend results in the rear view mirror.

With that in mind, we run you through all the action ahead of what promises to be another unpredictable, dramatic week of Champions League action. Will anyone seal their place in the knockout stages already?

Jump to groups:
- Tuesday's matches: E | F | G | H
- Wednesday's matches: A | B | C | D

GROUP A: Bayern Munich, Atletico Madrid, FC Salzburg, Lokomotiv Moscow

Standings: Bayern (9 pts), Atletico Madrid (4 pts), Lokomotiv Moscow (2 pt), FC Salzburg (1 pt)

ATLETICO MADRID vs. LOKOMOTIV MOSCOW

Wednesday, 3 p.m. ET / 8 p.m. GMT

Diego Simeone got his first ever win over Barcelona as Atletico Madrid boss on Saturday thanks to Yannick Carrasco's first-half goal but they need a win on Wednesday to keep up their Champions League charge. Luis Suarez and Lucas Torreira will miss out due to positive COVID-19 tests, while Hector Herrera has a muscle injury. But Diego Costa returned against Barcelona and will lead the line on Tuesday.

Lokomotiv won 1-0 against Arsenal Tula on Saturday thanks to Anton Miranchuk's second-half goal, while Vedran Corluka saw red. They have two wins from their first three Champions League matches and have a hefty injury list which includes Mikhail Lysov, Boris Rotenberg, Dmitri Barinov, Stanislav Magkeev and Fedor Smolov. Atletico will be clear favourites to win this one.

BAYERN MUNICH vs. FC SALZBURG

Wednesday, 3 p.m. ET / 8 p.m. GMT

Bayern Munich have a perfect record in the Champions League with three wins from three, but drew 1-1 at the weekend at home to Werder Bremen, with Kingsley Coman's second-half goal enough to earn them a point. But they will be optimistic of getting back to winning ways against Salzburg, whom they beat 6-2 in the reverse fixture. Niklas Sule is a fitness doubt, while Alphonso Davies, Joshua Kimmich and Corentin Tolisso will all be absent.

FC Salzburg are dominating the Austrian Bundesliga but suffered a surprise 3-1 defeat at home to Sturm Graz on Saturday with Mergim Berisha scoring their only goal. Manager Jesse Marsch said the result was down to Sturm Graz having more character and he'll look for a response against the Champions League holders on Wednesday. Star striker Patson Daka remains injured while Youba Diarra, Antoine Bernede and Ousmane Diakite will also miss out. Bayern should take this one.

GROUP B: Real Madrid, Shakhtar Donetsk, Inter Milan, Borussia Monchengladbach

Standings: Borussia Monchengladbach (5 pts), Shakhtar Donetsk (4 pts), Real Madrid (4 pt), Inter (2 pts)

BORUSSIA MONCHENGLADBACH vs. SHAKHTAR DONETSK

Wednesday, 12:55 p.m. ET / 5:55 p.m. ET

Gladbach drew 1-1 at home at Augsburg on Saturday with Florian Neuhaus' first-half goal only enough to earn them a point. It was a poor result for Marco Rose's side, but they still have Ramy Bensebaini and Alassane Plea absent due to COVID-19 protocols. But they are at the top of Group B with a win and two draws and will hope to have the upper hand against Shakhtar Donetsk.

The Ukrainians started this campaign brilliantly with their memorable win over Inter Milan but fell to a heavy 6-0 defeat in the last round to Gladbach. They drew 1-1 at the weekend with FC Oleksandriya, with Dodo scoring, but they'll be without Ismaily, Viktor Kornienko, Maksym Malyshev, Viktor Kovalenko and Yevhen Konoplyanka for Wednesday.

INTER MILAN vs. REAL MADRID

Wednesday, 3 p.m. ET / 8 p.m. GMT

Antonio Conte's side have just two points from their first three matches in the Champions League but won handsomely at the weekend, beating Torino 4-2 thanks to goals from Alexis Sanchez, Lautaro Martinez and a brace from the outstanding Romelu Lukaku. Aleksandar Kolarov, Stefano Sensi and Matias Vecino will all miss out.

Zinedine Zidane's Real Madrid drew 1-1 at Villarreal on Saturday and sit fourth in La Liga. Sergio Ramos will miss out with a hamstring injury, with Karim Benzema a doubt. Casemiro and Eder Militao will need fresh COVID-19 tests and negative results to be permitted to play while Luka Jovic will miss out after he returned a positive result. Federico Valverde and Alvaro Odriozola are long-term absentees. We think this will end in a draw.

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GROUP C: FC Porto, Manchester City, Olympiakos, Marseille

Standings: Man City (9 pts), FC Porto (6 pts), Olympiakos (3 pts), Marseille (0 pts)

OLYMPIAKOS vs. MANCHESTER CITY

Wednesday, 12.55 p.m. ET / 5.55 p.m. GMT

The Greek side won 1-0 at Panathinaikos on Saturday thanks to Kostas Fortounis' goal but will be without Ousseynou Ba for Wednesday's game. They have one win from three in the Champions League -- which came against Marseille in round one -- but will be wary of a wounded Manchester City side.

Pep Guardiola's team lost 2-0 at Tottenham Hotspur at the weekend in the Premier League but are in control of Group C with three wins from three. Nathan Ake, Sergio Aguero and Fernandinho are all out, while Benjamin Mendy is an injury doubt. But Guardiola's team should come away from Greece with a victory.

MARSEILLE vs. FC PORTO

Wednesday, 3 p.m. ET / 8 p.m. GMT

Marseille have lost three from three in the Champions League and had their Ligue 1 match against Nice postponed at the weekend due to a number of positive COVID-19 results from their opponents. Andre Villas-Boas' last competitive match was back on Nov. 6 against Strasbourg but that break has allowed Hiroki Sakai and Alvaro Gonzalez to return to full fitness.

FC Porto lost their opening Champions League match to Manchester City but have since won back-to-back group games. They won 2-0 at GB Fabril in the Taca de Portugal with Toni Martinez and Mehdi Taremi scoring, but have concerns in defence ahead of their trip to France with Mouhamed Mbaye, Ivan Marcano and Pepe absent. Mark this one down for a draw.

GROUP D: Liverpool, Ajax, Atalanta, FC Midtjylland

Standings: Liverpool (9 pts), Ajax (4 pts), Atalanta (4 pts), FC Midtjylland (0 pts)

AJAX vs. FC MIDTJYLLAND

Wednesday, 3 p.m. ET / 8 p.m. GMT

Ajax were at their dominant best on Sunday as they beat Heracles 5-0 in the Eredivisie with Lassina Traore, David Neres and Dusan Tadic scoring alongside a brace from Zakaria Labyad. They have a win, draw and a loss so far in Group D and are without long-term absentee Mohammed Kudus and winger Antony.

The Danish champions are yet to get off the mark in the Champions League with zero points from their first three matches but are riding high in the Danish Superliga with six wins from their first nine games. They won 2-1 at AGF on Sunday with Frank Onyeka and Sory Kaba both scoring. Evander will miss out through injury, but Ajax should have too much and will get their second win in this European campaign.

LIVERPOOL vs. ATALANTA

Wednesday, 3 p.m. ET / 8 p.m. GMT

Despite Liverpool's ever-growing injury list, Jurgen Klopp's men won 3-0 against Leicester City on Sunday with Diogo Jota again brilliant. The Portuguese forward grabbed one goal alongside Roberto Firmino's effort and an own goal from Jonny Evans. Liverpool are playing brilliantly in the Champions League with three wins from three, but are without Virgil van Dijk and Joe Gomez, while Mo Salah is a doubt as he returns from COVID-19 and Thiago is still recovering from his knee injury.

Atalanta drew 0-0 at Spezia on Saturday and are having a difficult 2020-21 season with four wins from their first eight in Serie A. And in the Champions League they are the picture of inconsistency having won one, drawn one, and losing to Liverpool 5-0 last time out. Mattia Caldara remains a long-term absentee and we feel Klopp's side should have too much for Atalanta.

GROUP E: Sevilla, Chelsea, Krasnodar, Rennes

Standings: Chelsea (7 pts), Sevilla (7 pts), Krasnodar (1 pt), Rennes (1 pt)

STADE RENNES vs. CHELSEA

Tuesday, 12.55 p.m. ET / 5.55 p.m. GMT

Rennes are rooted to the foot of Group E with just one draw from their first three matches and they will still be smarting from their 1-0 defeat to Bordeaux on Friday in Ligue 1. Against Chelsea, they lost the return fixture 3-0 at Stamford Bridge last time around and will be without star defender Daniele Rugani, plus Jonas Martin and Faitout Maouassa for Tuesday.

Chelsea head to France buoyed by their 2-0 win at Newcastle on Saturday where Tammy Abraham scored alongside an own goal from Federico Fernandez. They are bubbling nicely under Frank Lampard and sit third in the Premier League with 18 points from their first nine matches. Christian Pulisic remains an injury concern for Chelsea, while Kai Havertz and Thiago Silva are also likely to miss out but Lampard's men should have too much for Rennes.

KRASNODAR vs. SEVILLA

Tuesday, 12.55 p.m. ET / 5.55 p.m. GMT

Krasnodar are having a mixed season but will hope their 1-0 win over Tamov on Saturday, thanks to Remy Cabella's goal, will be the sign of better things to come. They have one point from their first three Champions League matches and will be without Sergey Petrov and Matvey Safonov for Tuesday's match.

Sevilla are sweating on left-back Marcos Acuna's fitness after he limped off in their 4-2 win over Celta Vigo on Saturday. Jules Kounde, Youssef En-Nesyri, Sergio Escudero and Munir all scored for Julen Lopetegui's men at the weekend, but they are still yet to hit top form in La Liga this term. Yassine Bounou will likely miss out due to COVID-19 while Suso is also absent but they will be optimistic of taking all three points on Tuesday evening.

GROUP F: Zenit St. Petersburg, Borussia Dortmund, Lazio, Club Brugge

Standings: Dortmund (6 pts), Lazio (5 pts), Club Brugge (4 pts), Zenit (1 pts)

LAZIO vs. ZENIT ST. PETERSBURG

Tuesday, 12:55 p.m. ET / 5:55 p.m. GMT

Simone Inzaghi's men won 2-0 at Crotone on Saturday with Ciro Immobile scoring his fifth of the season and Joaquin Correa adding another. They have a win and two draws from their first three matches in the Champions League but will be without star midfielder Sergej Milinkovic-Savic and Luiz Felipe due to COVID-19, while veteran Pepe Reina is favourite to continue in goal.

Zenit are still in the mix for the Russian Premier League, and sit second in the standings after their 2-2 draw with Akhmat Grozny on Saturday where both Daler Kuzyaev and Dejan Lovren scored. They have just one point from their first three games in the Champions League however, but have a number of injury doubts with Vyacheslav Karavaev, Sardar Azmoun, Sebastian Driussi and Magomed Ozdoev all likely to miss out. This should be a home win.

BORUSSIA DORTMUND vs. CLUB BRUGGE

Tuesday, 3 p.m. ET / 8 p.m. GMT

Dortmund hammered Hertha Berlin 5-2 on Saturday with Golden Boy Erling Haaland scoring four, alongside another from Raphael Guerreiro. They also gave 16-year-old wonderkid Youssoufa Moukoko his debut, who could become the youngest player in Champions League history if he features on Tuesday. Dortmund will be without Dan-Axel Zagadou and Marcel Schmelzer but will be favourites for against the Belgians.

Club Brugge have drawn three of their last five but just edged past KV Kortrijk on Saturday thanks to on-loan Noa Lang's winner. They have four points from nine in the Champions League but have a strong squad to pick from with only Eduard Sobol, Federico Ricca and Matej Mitrovic absent.

GROUP G: Juventus, Barcelona, Dynamo Kiev, Ferencvaros

Standings: Barcelona (9 pts), Juventus (6 pts), Dynamo Kiev (1 pt), Ferencvaros (1 pt)

DYNAMO KIEV vs. BARCELONA

Tuesday, 3 p.m. ET / 8 p.m. GMT

Dynamo Kiev have just one draw from their first three matches but come into Tuesday's match off the back of a 2-0 win over Inhulets with Denys Harmash and Mykola Shaparenko scoring. But Kiev are still in the midst of a COVID-19 crisis and have a number of first-team players absent, along with injured contingent Mykyta Burda, Oleksandr Tymchyk and Nazariy Rusyn.

Barcelona have rested Lionel Messi for the trip to Ukraine, while they have their own injury crisis with Gerard Pique and Sergi Roberto long-term absentees. Clement Lenglet is their only fit centre-back, and they have rested Frenkie de Jong. Sergio Busquets is also out, Ansu Fati is injured, but Ousmane Dembele is available. Even without their absent contingent, they should make it four from four with a win in Ukraine.

JUVENTUS vs. FERENCVAROS

Tuesday, 3 p.m. ET / 8 p.m. GMT

Juventus are hot on the heels of Barcelona in Group G and will hope to take momentum from their 2-0 win over Cagliari at the weekend, where Cristiano Ronaldo scored twice. They will be without Leonardo Bonucci and Aaron Ramsey, while Federico Chiesa and Giorgio Chiellini are both doubts.

Ferencvaros are unbeaten at the top of the Nemzeti Bajnoksag I with seven wins and two draws from nine, but have struggled in the Champions League with just one point from four. Their last match against Juventus ended in a 4-1 win for Andrea Pirlo's side, so the odds are stacked in the hosts' favour.

GROUP H: Paris Saint-Germain, Manchester United, RB Leipzig, Istanbul Basaksehir

Standings: Man United (6 pts), RB Leipzig (6 pts), PSG (3 pts), Istanbul Basaksehir (3 pts)

MANCHESTER UNITED vs. ISTANBUL BASAKSEHIR

Tuesday, 12:55 p.m. ET / 5:55 p.m. GMT

United's rollercoaster season continued at the weekend with a controversial 1-0 win over West Brom at Old Trafford, thanks to Bruno Fernandes' penalty. They sit above Manchester City in the Premier League, but Ole Gunnar Solskjaer's side are under pressure to perform having suffered a surprise defeat to Basaksehir last time out. Alex Telles made his return after testing positive for COVID-19 at the weekend, but Eric Bailly and Luke Shaw will miss out.

Basaksehir lost to local rivals Besiktas at the weekend 3-2, with Fredrik Gulbrandsen scoring a late brace after they were reduced to 10 men with Mehmet Topal sent off. Their surprise win over United is their sole victory in the Champions League group stages so far and they will have Mert Gunok and Danijel Aleksic both absent due to COVID-19. Expect Manchester United to win this one.

PARIS SAINT-GERMAIN vs. RB LEIPZIG

Tuesday, 3 p.m. ET / 8 p.m. GMT

PSG lost 3-2 at Monaco on Friday in an eventful game where Kylian Mbappe scored twice, but a double from Kevin Volland, a penalty from Cesc Fabregas and a red card for PSG's Abdou Diallo saw Thomas Tuchel's men suffer their third league defeat of the season. They still sit proudly at the top of Ligue 1, but need wins in the Champions League with three points from their first three matches. Neymar is set to start for PSG, while Ander Herrera and Marco Verrati are doubts; Moise Kean is sidelined while Mauro Icardi, Idrissa Gueye and Mauro Icardi are all out.

RB Leipzig squandered their chance to go top of the Bundesliga at the weekend, as they drew 1-1 at Eintracht Frankfurt with Yussuf Poulsen scoring. In the Champions League they are two wins from three but have injury doubts over Nordi Mukiele, Lukas Klostermann, Marcel Halstenberg, Konrad Laimer and Hwang Hee-Chan. We think PSG will edge this.