Matchday two of the 2023-24 Women's Champions League group stage is over and yet again the underdogs showed they mean business this season.

Swedish side BK Häcken and Norway's SK Brann both made it two wins from two having been unfancied. Häcken's win came at home to Real Madrid, who had scored first and have now picked up just one point from their opening two fixtures. Brann got the better of Slavia Prague 1-0. Barcelona, though, made no mistake in coming from behind to beat Eintracht Frankfurt 3-1.

For the second gameweek running, both Parisian clubs were beaten, as Paris Saint-Germain lost 1-0 to Bayern Munich and Paris FC were thrashed 4-1 at Chelsea, with Sam Kerr scoring a hat trick.

Elsewhere, Lyon beat St. Pölten 2-0 and Benfica claimed a 1-0 win over Rosengard on Wednesday. And then on Thursday, Roma soundly beat Ajax Amsterdam 3-0.

We asked our writers Sophie Lawson, Sam Marsden and Tom Hamilton to answer some of our burning questions.

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1. Which team is already in trouble?

Sam Marsden: It's obvious, but it's hard to look further than Paris Saint-Germain. The French side have made five consecutive quarterfinals -- reaching the semifinals in three of those years -- but have zero points after two matches. That said, I wouldn't rule them out yet.

With back-to-back games to come against Roma, they could still haul themselves back into contention to get out of an extremely competitive group. Roma once again showed their quality with a comfortable win over Ajax on Thursday, but with a squad filled with talent, PSG should still back themselves to beat the Italians -- if they are at their best.

Tom Hamilton: Real Madrid and Paris Saint-Germain are both in trouble. Real Madrid were lucky to draw at home with Chelsea last time around and suffered a shock 2-1 defeat at BK Häcken on Thursday. They had plenty of first-half chances through Signe Bruun, but although she opened the scoring early on, she had two other great opportunities to stretch their advantage. With a doubleheader against wounded Paris FC and a trip to Chelsea to come, they are in trouble.

Bayern Munich drew with Roma last time out, and traveled to PSG, who were smarting from their opening-round 2-0 loss at Ajax. PSG would have hoped to get things back on track against Bayern but instead fell to a 1-0 defeat, leaving them pointless after two matches. PSG looked troubled early on, as a wayward defensive header was held out only by a scrambling-back Katarzyna Kiedrzynek, while Klara Bühl had a shot well-saved. Magdalena Eriksson got the winner for Bayern after 21 minutes with a close-range finish, but PSG had only a series of half-chances, with Maria Luisa Grohs producing a decent save from Tabitha Chawinga in the second half. It's looking ominous for the Parisians.

Sophie Lawson: Two games in and five of the 16 teams have yet to pick up a point. Given the groups, perhaps it's not such a surprise to see Rosengard propping up Group A, or St. Pölten yet to have points on the board. But Paris Saint-Germain languishing without a point in Group C can't be ignored.

The loss to Ajax last week was the surprise of the round, and on Thursday night, at home to Bayern Munich, they were underwhelming and lost again, 1-0. It wasn't all bad from PSG, but they were flat in attack with a real disconnect between the front line and the midfield. After losing in Amsterdam, a response was vital and it simply wasn't forthcoming.

Likewise, after such a sorry showing in the league against Barcelona last weekend, where Real Madrid were thrashed 5-0, a reaction was expected against BK Häcken. But Las Blancas were second best and lost 2-1, despite taking the lead early in the game. Poor displays from the Liga F runners-up can happen, in Europe or in Spain, but with such lavish resources they shouldn't be struggling against the Swedish club with much less experience on the biggest stage.

2. Nobody gave Häcken a hope in a tough Group D. Are they the biggest shock so far?

Hamilton: It was a historic night in Gothenburg, as Häcken got their first-ever home Champions League group stage win. Both goals were wonderfully worked with Rosa Kafaji timing her run to perfection to hammer home the equaliser in the 59th minute, and then Katarina Kosola finding the top corner from the edge of the box for the winner after 76 minutes. The scenes at full-time as the bench ran onto the pitch to hug their stunned and exhilarated teammates showed how much it meant. They're now two from two off the back of their win against Paris FC and will fancy their chances of making the final eight.

But when judging the biggest upset, don't forget Paris FC's role in the qualifiers as they knocked out both Arsenal and Wolfsburg, two teams with far bigger budgets and European pedigree. They got past Arsenal on penalties, but their two-legged triumph over Wolfsburg was down to brilliant management and persistence.

Eintracht Frankfurt threatened the upset of the tournament on Wednesday as they held a 1-0 lead against Barcelona heading into the break, only to lose 3-1, while SK Brann's form might surprise a few with back-to-back 1-0 wins.

Ajax got their first Champions League group stage win last week against PSG, but they've been knocking on the door for a while. So for me, Paris FC's two wins over Arsenal and Wolfsburg are still the most eye-catching results so far.

Lawson: Häcken's ability to roll with the punches and show some of their best football has been such a welcome surprise. This is a team who lost their coach, Robert Vilahamn, over the summer and had to adapt to his replacement, Mak Lind. They lost out on the Swedish title to Hammarby this month on goal difference, but there's been no hanging of heads.

It helps that Häcken boast one of the more exciting young attackers in Sweden in 20-year-old Kafaji, but their two wins so far have been team efforts; this is a team of battlers. What was impressive in their win over Real Madrid was how positively they played at home. Even after going a goal down, there was no fear or holding back. In European football, historically not a happy hunting ground of Häcken, including in their earlier outings when they were known as Kopparbergs/Göteborg, it's easy for teams to play conservatively, but Lind seems to believe in his players' abilities. That calm and confidence has been the biggest surprise.

SK Brann's two wins from two is also well worthy of praise. Similarly, they had a change of manager earlier in the season (bringing in Martin Ho from Manchester United after Olli Harder left) and finished a distant fourth in the 2023 Toppserien. But the Norwegians have played smartly in both outings (against St. Pölten and Slavia Prague). Even though they had to dig in and ride their luck, their maturity in their debut season has been refreshing.

Marsden: With everyone looking at Chelsea and Real Madrid, BK Häcken have snuck to the top of the group after two games. Even Paris FC, after stunning Arsenal and Wolfsburg in qualifying, were more fancied going into the tournament.

Striker Kafaji was brilliant in Häcken's win over Madrid, scoring for the third consecutive game, and they have got themselves into a great position going into their doubleheader with Chelsea in December. Brann, also with two wins from two, have made an eye-catching start, too. It's good to see the Scandinavian sides doing well given their historic success in the women's game before other clubs started pouring money into it.

3. Which player has exceeded expectations?

Lawson: Of the 176 starters across the eight games, it's hard to follow each individual and critique all of their inputs, but here are three players who aren't likely to grab the headlines but who all impressed.

While yet to keep a clean sheet, 20-year-old goalkeeper Angel Mukasa has still managed to excel for Rosengard. Against Benfica on Wednesday, she came up with some big saves and looked to organise her back line well despite being under heavy pressure. It's been a forgettable season for the former Swedish champions, who ended up finishing the season in seventh place, and their Champions League group is highly unforgiving. Mukasa is a goalkeeper who has been worked but still impressed.

Jackie Groenen deserves a lot of praise for her industrious work in Paris. The hero over the weekend with her stoppage-time winner against Fleury, a real stunner from the Netherlands international, Groenen was at the heart of so much of PSG's better attacking play whilst patrolling midfield to snuff out Bayern's attacks. For how well she's playing and how key she is, if there's any player PSG would want to stick in the cloning machine, it's Groenen.

Roma are a joy to watch and it's easy enough to pick out any of the Giallorosse, but Emilie Haavi has been excellent since moving to the Italian club from LSK Kvinner two years ago. For as good as Haavi is in Serie A, her consistency and work rate when Roma are in European competition is always worthy of praise. And at the Tre Fontante on Thursday night, she again put in a breathless performance, running the channel all night against Ajax and bagging an assist for Manuela Giugliano's memorable volley. It's no less than you'd expect of the 31-year-old.

Marsden: They may have lost to Barcelona, but Eintracht Frankfurt gave the holders a scare in the first half, with Laura Freigang the pick of their players. She scored the goal that gave the German side a surprise lead at the break and threatened every time they countered. Frankfurt lost their shape in the second period and were well-beaten in the end, but, led by Freigang, they will feel confident of beating Benfica and Rosengard to second place in the group.

One of Barça's comeback goals, meanwhile, was scored by Mariona Caldentey. It's hard to say she's exceeding expectations given she has now scored in eight consecutive Champions League campaigns, but there is increasingly a feeling her brilliance is underestimated outside of Barça.

Hamilton: If you're looking for a moment where an individual saved her team, then look no further than the remarkable double save Benfica keeper Lena Pauels pulled off in the closing stages of their win over Rosengard. It was in the 82nd minute of the match as Rosengard pushed for an equaliser. A cross found Mai Kadowaki in plenty of space at the back post, but Pauels managed to pull off a brilliant reaction stop and then blocked the follow-up from Bea Sprung. It kept Rosengard at bay and secured the three points for Benfica.

Elsewhere, there was a brilliant goalkeeping performance from Aurora Mikalsen for Brann as she managed to keep out Slavia Prague for their 1-0 win. Daniëlle van de Donk was magnificent for Lyon in a formidable midfield trio alongside Damaris Egurrola and Lindsey Horan in the 2-0 victory over St. Pölten, but their standout player was left-back Selma Bacha.

But, and bear with me here, if you're looking for someone who pleasantly surprised, then Sam Kerr's hat trick against Paris FC was truly remarkable. Is the Australia international exceeding expectations? Well, strictly speaking no, because she's one of the best players in the world, but factor in the summer she had where she wore the weight of a country's expectations in the World Cup, had to battle through injury and is still putting in match-winning performances having barely had a chance to breathe.

The schedule is merciless for Chelsea as they continue to chase four trophies, but Kerr's treble was outstanding. The first two saw her striker's instinct pay off as she darted in to knock home brilliant crosses from Lauren James and then Johanna Kaneryd while her third was a trademark audacious Kerr lob from outside the box which had Chiamaka Nnadozie scrambling. Each a great goal in their own right which brought up her eighth hat trick in Chelsea colours.

And what makes it even more remarkable? Post-match Emma Hayes revealed Kerr is still managing an injury. "If that's her at 80%, I can't wait for the 100%," Hayes said. "She's so incisive with her movement. The third goal when she lobbed it was brilliant centre-forward play. I don't know anyone who puts the ball away like she does."