It has been one of the most open and unpredictable seasons in Premier League history. Nine different teams have been top at various points in the campaign, all of the big clubs have suffered unexpected defeats, and every side in the top 10 still has a chance of qualifying for the Champions League. But as the season heads into its final third, Manchester City have emerged from the pack to take control and establish a vice-like grip on top spot.

Uncertainty seems to have been banished at the Etihad Stadium, with Pep Guardiola's team becoming the first English side to win 17 consecutive games in all competitions, outscoring opponents 46-6 over that span. They also broke Man United's Premier League record of nine consecutive wins to open the calendar year, beating Everton 3-1 on Wednesday night for their 10th victory in 2021.

In November, City dropped to 11th in the table, eight points behind leaders Tottenham Hotspur, after a 2-0 defeat away to Jose Mourinho's team. They seemed to be in crisis, having made their worst start a season in more than 10 years. But three months on, they are 10 points clear at the top, with 14 games remaining, and are on course for a quadruple.

How has the Premier League been turned on its head in such a short period of time? It's not just about what City have done; their surge back to the top is as much down to the failings of others as the improvement of Guardiola's team. Here are seven factors behind the "end" of the title race for 2020-21.

1. Man City's defensive renaissance

Following that 2-0 defeat at Spurs, City's goals-against column read 11 conceded in eight games. Having scored just 10 themselves, Guardiola's side were in the unfamiliar situation of having a negative goal difference. So Guardiola made a change, bringing in John Stones in place of Aymeric Laporte to partner Ruben Dias at centre-half, and City haven't looked back since.

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Stones has struggled for form and fitness during the past two seasons at City and looked to be heading for the exit door. Laporte and Dias had been Guardiola's anticipated defensive double act, but Laporte has since been unable to reclaim his place -- starting three times at centre-half in the league since the Spurs defeat -- with Stones and Dias building a formidable partnership. Since that loss, Stones and Dias have played together 13 times in the league and City have conceded just three goals in that run.

Every title-winning team needs to have a reliable defence, and City now have that thanks to Stones and Dias.

2. Gundogan's goals

Ilkay Gundogan has often divided opinion among City supporters. Many fans regard the Germany midfielder as too passive and negative in possession, while others value his ability to keep the ball and provide a reliable launch pad for the team's numerous attacking talents. But the 30-year-old has been given a more advanced role by Guardiola this season, deviating from his old position in defensive midfield. The result has been a run of goals, with Gundogan scoring more in the Premier League (11) than any other player in the division since the beginning of December.

Remarkably, he's City's leading scorer in the Premier League, and his goals have more than made up for drop in output by Kevin De Bruyne, who had scored just three prior to his latest injury. Gundogan's goal streak has coincided with City's winning run, with his brace in the 4-1 win at Liverpool perhaps the most important.

3. Liverpool's Anfield anguish

When Roberto Firmino headed in a 90th-minute winner for Liverpool against Spurs at Anfield on Dec. 16, it seemed to be a pivotal result in the title race. Spurs started the game as league leaders, but the defending champions claimed a 2-1 win and it sent them top, eight points clear of eighth-placed City. But since that win, Liverpool have been in relegation form at Anfield, failing to win any of their five Premier League games on home soil.

A 1-1 draw against West Bromwich Albion was followed by a goal-less stalemate against Manchester United, but at least their unbeaten Anfield run, dating back to April 2017, was still intact. Yet even that 68-game unbeaten league streak at home was ended with a 1-0 loss to Burnley, with Brighton & Hove Albion and City both winning at Anfield since to prove it's no longer an impregnable fortress.

By collecting just two points from a possible 15 at Anfield since mid-December, Liverpool have made it easy for City to leave them trailing in their wake.

4. Tottenham, Mourinho also fall away

Remember when Tottenham were threatening to win their first league title since 1961? Maybe not, but it was only two months ago that Mourinho's team were top of the table having gone unbeaten since the opening day of the season.

At the time, Spurs had gone 11 games without defeat in the league and recorded wins against Man United, City and Arsenal, but the wheels began to come off during a 1-1 draw at Crystal Palace on Dec. 13, when the home side netted a late equaliser. From that point on, Spurs have banked just 11 points from a possible 33 and dropped out of the top four entirely.

All talk of a title at the Tottenham Hotspur Stadium has naturally been silenced, with the priority now simply to secure a Champions League spot.

5. De Gea lets United down

Few would have tipped Manchester United to be a serious title contender this season, but Ole Gunnar Solskjaer's team went top in January with a 1-0 win at Burnley and they were still top after the 0-0 draw at Liverpool on Jan. 17. But every team is only as strong as its weakest link, and the prolonged concerns over the reliability of goalkeeper David de Gea have been borne out in recent weeks. The Spain No. 1 proved culpable in the shock 2-1 defeat at home to Sheffield United, and then again thanks to two costly errors during the 3-3 Old Trafford draw against Everton.

De Gea's mistakes in both games arguably cost United five points -- he was not the only player at fault, of course, though his errors were decisive -- and the failure to win those two home fixtures has seen Solskjaer's side fall 10 points behind City after 24 games. They still have to play Guardiola's team at the Etihad in early March, but United's margin for error has evaporated and City have ruthlessly taken advantage.

6. The "two-week COVID break" rant

Liverpool manager Jurgen Klopp sparked a pre-match war of words with Guardiola ahead of the 4-1 defeat against City by claiming that the leaders had benefited from a "two-week break because of COVID-19" at the end of December.

Klopp's incendiary comments hinged on City's trip to Everton getting postponed on Dec. 28 due to a COVID-19 outbreak at the club's training ground that led to an unspecified number of positive tests. That game was called off just four hours before kickoff, albeit with Everton demanding full disclosure of the information City provided to the Premier League to justify the postponement.

By having the game postponed, City avoided having to play twice in 48 hours after facing Newcastle on Dec. 26, but they were unable to name a full subs bench at Chelsea on Jan. 3 due to the impact of the COVID outbreak. The situation gave City an eight-day break without a game at the end of December -- Liverpool played three games during the same period -- prompting Klopp to bemoan his team's lack of a similar break.

Whether it played in City's favour or not, Guardiola's team have since won 14 straight games in all competitions.

7. Ending the Anfield jinx

City had already claimed top spot in the Premier League before their trip to Liverpool on Feb. 7, but the manner of their 4-1 victory emphasised the growing confidence in Guardiola's squad.

Winning at Anfield ended City's 18-year wait for a victory at Liverpool, and they did it by scoring four goals at the stadium for the first time since 1937. But City also targeted the weaknesses in the Liverpool team by exposing the defensive frailties of full-backs Andy Robertson and Trent Alexander-Arnold, and using the pace and movement of Phil Foden to cause disarray in the opposition half.

It was a performance and victory of champions, a swing of the pendulum back towards the Etihad, and the end result showed why Guardiola's team are firmly on course to dethrone Liverpool as kings of the Premier League.