Chelsea neutralized the Premier League 's most rampant attack in beating title rival Manchester City 1-0 on Monday, with Branislav Ivanovic's first-half goal ending the deposed leaders' 100 percent winning record at home.
Ivanovic lashed home a fierce 25-yard shot in the 31st minute to cap a brilliant counter-attacking display by the visitors, who defended supremely against a team that has already scored 115 goals this season in all competitions.
It was the first time City failed to score at home in the league since November 2010 - a streak of 61 matches - and the hosts were lucky not to lose by an even bigger margin, with Chelsea hitting the goal frame three times and threatening almost every time they broke forward.
Chelsea knew a defeat at Etihad Stadium - where City had won all of its 15 domestic games this season and lost only to Bayern Munich in the Champions League - would leave it six points behind City and potentially out of the title reckoning.
Now, after completing the double over most pundits' title favorites, Jose Mourinho's side is level on points with second-place City, putting Arsenal back on top with a two-point lead.
''We beat them twice but they are the best team,'' Mourinho said of City, adding that he left the club's masseur, Billy McCulloch, to do the pre-match team talk. ''It's (a title race between) two horses and a little horse. A little horse that still needs milk.''
Mourinho is renowned around the football world as the master defensive strategist. Few will forget how his Inter Milan side nullified Barcelona in the 2010 Champions League semifinal at the Camp Nou, while Chelsea has already ground out 0-0 draws at Manchester United and Arsenal this season.
It was different here, though. Chelsea counter-attacked with such pace and purpose, and hounded City's much-lauded ball-players into sloppy mistakes, that the visitors could easily have won by three goals. Samuel Eto'o hit the bar and the excellent Nemanja Matic and Gary Cahill struck the post.
City badly missed the injured Sergio Aguero but also holding midfielder Fernandinho, who was ruled out at the last minute with a muscle injury. Martin Demichelis - a center back - filled in in central midfield and couldn't stop Chelsea's midfielders running amok.
''We had five or six players (missing) so maybe this defeat doesn't have a bad psychological effect,'' Pellegrini said. ''I think that for Chelsea it was a decisive game, but not for us.''
Before Ivanovic put Chelsea in front, Ramires had a curling shot saved after running onto a pass from Willian, who had led a 4-on-1 attack on City's beleaguered defense.
The goal arrived soon after, with City captain Vincent Kompany diving to block Ramires' shot but seeing the ball squirt out to Ivanovic, who drove a powerful first-time shot with his left foot into the bottom corner.
And moments before halftime, Eden Hazard skirted round Pablo Zabaleta and crossed for Eto'o to smash a shot against the top of the bar.
City's defensive frailties were being exposed but the hosts were also quiet - by their standards - going forward. Alvaro Negredo was virtually anonymous, although Pellegrini later said the striker wasn't 100 percent, and the only attacking thrusts were provided by Yaya Toure, who curled one shot over, set up David Silva for a great chance that was glanced just wide and just missed a fizzing cross from Aleksandr Kolarov.
Mourinho had City just where he wanted them - and it almost got worse for Pellegrini's side when Matic strode forward and crashed a 30-yard effort against the post. Cahill then leapt to meet Willian's corner with a header that cannoned off the post, further incensing the home crowd.
City was reeling but finished strongly, with Silva denied by Petr Cech from a free kick then sidefooting wide from Kolarov's cross. And in the final seconds, substitute Stevan Jovetic's long-range shot was tipped over by Cech.
Arsenal, Manchester United and Tottenham - among others - have all been crushed by City at the Etihad this season. Chelsea, and expert strategist Mourinho, showed just how City can be stopped.