By Toby Davis
(Reuters) - Manchester City rediscovered their swagger to beat Chelsea 2-0 and move into the FA Cup quarter-finals on Saturday with Manuel Pellegrini winning the battle of tactical wits against Jose Mourinho.
Stevan Jovetic and Samir Nasri scored either side of halftime for City as Pellegrini finally fell upon a winning formula to get one over his managerial rival having lost both Premier League fixtures this season.
"We wanted revenge today," City captain Vincent Kompany told ITV sport.
"From the word go we were hard in the challenges and we did not give them anything. It is a good victory from us."
The result completed a difficult week for Mourinho, whose side drew with West Bromwich Albion in the league on Tuesday, and returned City to winning ways after their defeat by Chelsea 12 days ago was followed by a draw with Norwich City.
City, who had drawn a blank in their previous two games having scored more than 100 goals this season, will be joined in the draw for the last eight by holders Wigan Athletic and Sunderland.
Ben Watson, who grabbed the winner when Wigan shocked Manchester City in last year's final, continued his love affair with the competition by firing the second-tier side to a 2-1 upset victory at Premier League strugglers Cardiff City.
Sunderland punished Southampton for taking the competition too lightly and making a raft of changes, with a 1-0 defeat thanks to a stunning strike from Craig Gardner.
The Cup was an opportunity for City and Chelsea to enjoy a break from what is becoming an increasingly fraught title race.
Yet the encounter had a pinch of added spice after Mourinho had spent the buildup throwing verbal hand-grenades at all his managerial rivals.
Chelsea's success at the Etihad Stadium 12 days previously was hailed as a piece of inspired tactical maneuvering from their Portuguese coach and laid down the gauntlet to Pellegrini to come up with a response.
So into the City team came workhorse James Milner to shadow Chelsea's man-in-form Eden Hazard, while Javi Garcia featured in center midfield where Martin Demichelis had been exposed in the recent league reverse.
After some tentative probing from both sides, City took the lead with Jovetic making amends for firing over the bar from close range a minute earlier by sliding a precise finish into the corner after being fed by Edin Dzeko.
For Chelsea there were few positives in a poor first half in which they had one shot, a dismal effort from Willian that soared high over the crossbar into the crowd.
Mourinho, so often lauded for his game-changing substitutions, was also outmaneuvered on that front as Pellegrini brought Nasri off the bench to see him grab a second goal on 66 minutes.
A neat one-two with Silva ended with the Frenchman side-footing into an unguarded goal.
City had the ball in the net for a third time when Joleon Lescott bundled it home late on, but the linesman's flag prevented further damage for the visitors.
"The second goal was an offside but we would still have lost 1-0 as we were never close to scaring City in the game," Mourinho said.
"Today proved how difficult it is to win here, which shows how well my team did in the last game."
Wigan, who dropped out of the top flight after their Wembley success, took the lead after 18 minutes when Chris McCann turned in a low cross.
Cardiff, second bottom in the Premier League, leveled through Fraizer Campbell nine minutes later, but Watson restored the visitors' lead just before the break, firing into the top corner from 25 meters.
Sunderland, who have already reached the League Cup final, again put their Premier League struggles to one side with Gardner thundering a second-half shot into the top corner from 25 meters.
Southampton manager Mauricio Pochettino faced criticism for his team selection, however, after resting players despite being comfortably positioned in mid-table.
Sheffield Wednesday's home game with Championship rivals Charlton Athletic was called off because of a waterlogged pitch.
On Sunday, Arsenal host Liverpool, Swansea City travel to Everton and Championship side Nottingham Forest visit third tier Sheffield United.
Championship club Brighton and Hove Albion entertain Hull City on Monday.
(Reporting by Toby Davis; editing by Clare Lovell)