A superb goal from Kevin De Bruyne decided the contest between the Premier League's top two on Saturday and seemingly the destination of the championship, with Manchester City's 1-0 win over Chelsea moving them 13 points clear at the summit.
It was a game which had been billed as the last chance for Chelsea - and third-placed Liverpool - to keep the defending champions in sight but City were dominant, pinning their visitors back in their own half for long periods and they eventually produced the moment of quality to extend their remarkable winning streak in the league to 12 matches.
De Bruyne - famously sold on by Chelsea - spun away from N'Golo Kante on 70 minutes and bent a brilliant, trademark swerving shot inside the far post from 20 yards, his fifth goal against his former club.
"It's an important victory because we're playing against a big contender," City boss Pep Guardiola said afterwards. "When you get three points they can't get three points and it's one week less. But in January no one is champion."
City should have been ahead well before De Bruyne's strike, with Jack Grealish spurning a glorious opening after Mateo Kovacic had been caught in possession by De Bruyne. City's £100m man clipped his shot straight at the on-rushing Kepa five minutes before half-time, and still has just two Premier League goals to his name since his record-breaking summer transfer.
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Chelsea defended well but didn't have a shot in the first half, the first time that has happened in the Premier League under Thomas Tuchel. However, they had three in the opening four minutes of the second, with Romelu Lukaku drawing a fine stop from Ederson from his own one-on-one chance.
But the Belgian - who had powered past John Stones in the opening minutes - was too often starved of good service, with Hakim Ziyech and Marcos Alonso culpable of overhitting passes in brief moments when Chelsea looked like they could open up the best defence in the division.
In many ways, the game was similar to City's win at Stamford Bridge in September, with Tuchel constantly urging his smothered side to try to push up, but while he had spoken about not playing so deep this time, doing so isn't easy against Pep Guardiola's slick City team who bring intensity in and out of possession.
Chelsea got the better of City in last season's Champions League final but it would now take something extraordinary for them or Liverpool to prevent Guardiola making it four Premier League titles in the past five seasons.
Guardiola: We were incredible - but you don't win the title in January!
Pep Guardiola refused to get carried away with Man City's title chances, despite them moving 13 points clear at the top of the Premier League table - but he was happy to pour praise on his side after their win over Chelsea.
"The team were incredible, brilliant," he told BT Sport. "The way we played, everything we have done... We cannot forget the team we played against; they are European champions. When you are there on the touchline you realise how incredible they are. You try to find spaces, but they're not there."
He continued in his press conference: "I know how difficult they are, how well they defend and how well we played. They defended collectively amazing and we beat them on one transition.
"All players gave everything. Important victory because we're playing against a big contender."
Discussing the gap at the top and the importance of beating a title rival, he added: "When you get three points they can't get three points and it's one week less. But in January no one is champion. Liverpool have a game in hand [after Sunday's match against Brentford]. If they win against Leeds it's eight points and eight points in January is nothing.
"The players will keep their feet on the ground. I know them. We've been together six seasons. I know the competitors they are and how they celebrate the good moments, suffer the bad ones and how we behave in all these games this year.
"Of course people are going to say 'it's over' but they know it's not over. In January that's impossible. But 12 games in a row, winning, winning, winning. But there's not just the Premier League, there's the Champions League, the FA Cup, many titles still.
"But from 180 minutes against the European champions we conceded one shot on target."
Tuchel: We deserved a draw; Lukaku and attackers needed more precision
Thomas Tuchel refused to be too critical of his side after the defeat, pointing out that Chelsea had beaten City in similarly low-scoring games last season. But he did concede that "a lack of precision" in forward areas had been costly.
"The result is disappointing, yes, but this can happen when you play at City. I think we deserved a draw, we defended very well, didn't concede many big chances. There was one in the first half from a big mistake from us," he told BT Sport.
"Performance-wise was OK. Commitment-wise I'm absolutely OK with the performance, especially given we had to change our back three. We deserved a draw, it would have been a fair result, but we don't have it. We have won games like this against City, that's the way it is.
"We had eight or nine offensive transitions [in the first half] and zero touches in the box. That was a big problem today, offensive-wise, the performance of the front players. That was down to a lack of precision, timing, and composure. At a level like this, we lost too many balls too easily.
"[Was Lukaku getting enough service?] Sometimes he needs to do the service. He's included, he had many ball losses without any pressure and in very promising circumstances. He had a huge chance. He is included, we want to serve him but he is part of the team.
"The performance up front, we can do much, much better and we need to do better.
"[Is the title race over?] It is not my question to answer. We will never give up, but if City keeps on winning every game, nobody can catch them."
Man of the match: Kevin De Bruyne
There's something special about a player when their 'trademark goal' is a brilliant, bending shot from outside the box. But when De Bruyne spun away from N'Golo Kante and into space on the edge of the Chelsea area there felt some inevitability about where the ball would end up.
Perhaps Kepa should have done better, with this strike from De Bruyne not quite in the corner, but it was still a fine effort and a classy way to seal a victory which will be a hammer blow to the fading hopes of Chelsea and Liverpool that they could pull City back.
De Bruyne - who was also City's top chance creator and, surprisingly, dribbler, on Saturday - is on a roll, like his team as a whole. And the quality he brings to the pitch is irresistible at times.
"He has everything," Pep Guardiola told BT Sport afterwards. "He has been with me here from day one. Everything we have won, we have won together. I am going to push him to keep on doing more and more. He's a world-class player who has humility and is humble, it is not easy to find that."
Thomas Tuchel added in his press conference: "The individual quality of Kevin De Bruyne made the difference."
Analysis: Man City have raised the bar
Sky Sports' Peter Smith:
"It was first versus second but it didn't really look like that. Chelsea defended well and limited Manchester City to only a handful of chances but City were dominant throughout, barely gave their visitors a look-in at the other end, and won through some individual brilliance from Kevin De Bruyne.
"It was almost a repeat of their victory at Stamford Bridge in September and, after completing the double over Chelsea, the 13-point gap between City and their nearest challengers is huge. It's only January, after all.
"Liverpool could close that chasm if they win their games in hand, and they still have to go to the Etihad themselves, but a turnaround now looks highly unlikely.
"City are setting incredible standards right now - and it's no surprise others are struggling to keep up. They have the best attacking numbers and the best defensive record, too.
"The 15-game winning streak they put together over the winter period last season took them to the title and seemed unrepeatable but they're up to 12 wins on the spin now and motoring away from their rivals again.
"When other teams have faltered during this busy festive period, City have just kept on winning. Pep Guardiola said his side were facing an 'emergency' of injuries, illness and suspensions at the start of December. Fast forward a month and a half and they're on course to finish the season with over 95 points.
"No striker? No problem. A disrupted pre-season - City were the last Premier League club to return to the training ground - may have affected some performances earlier in the campaign, but they're in their groove now.
"Of course, the resources and depth of quality Guardiola can call on is substantial. But the relentless nature of this City team, and the way they've adapted to challenges they've faced, is down to mentality and coaching.
"A fourth Premier League title in five seasons seems a near-certainty now for a team and manager who have raised the bar."
What's next?
Manchester City are back in action next Saturday against Southampton, live on Sky Sports from 5pm; kick-off 5.30pm. Chelsea are away to Brighton on Tuesday night in an 8pm kick-off.