Frank Lampard struck four as Chelsea signalled their title intentions in spectacular style with a crushing 7-1 win over Aston Villa while Arsenal suffered an injury-time nightmare at St Andrew's.
Carlo Ancelotti raised eyebrows by leaving Didier Drogba on the bench but the result was the biggest win of his side's season and one which took them back to the Barclays Premier League summit.
And Chelsea's cause was further boosted when Arsene Wenger's men blew three hard-earned points against Birmingham, with Kevin Phillips cancelling out Samir Nasri's opener at the death.
Lampard opened the scoring for Chelsea in the 15th minute but nerves were evident in the way the home side allowed Villa to hit back and level when John Carew converted Ashley Young's cross in the 29th minute.
Lampard's penalty nudged his side back in front just before the break then Chelsea ran riot with a brace for Florent Malouda, one for Salomon Kalou and two more for Lampard, who notched his fifth career hat-trick in the process.
It was a different story for Arsenal who had to battle through every minute of their clash with Alex McLeish's men but looked to have clinched it when substitute Nasri rocketed home a right-foot shot nine minutes from time.
Home keeper Joe Hart had been in good form to deny Theo Walcott in the first half but Birmingham also had their chances and Scott Dann missed a simple rebound after Roger Johnson's flick-on had hit the crossbar.
Wenger's introduction of Nasri and Andrei Arshavin in the 69th minute breathed new life into the Gunners and looked to have paid off handsomely with Nasri and Cesc Fabregas coming close to adding a second.
But the visitors' title push suffered a major blow in the first minute of added time when an attempted clearance in the box struck Phillips and the ball proceeded to loop back over Manuel Almunia into the net.
Tottenham took a firmer grip on the final Champions League place with a 2-0 win over Portsmouth at White Hart Lane with Pompey old boys Peter Crouch and Niko Kranjcar grabbing the goals.
Crouch headed home a Gareth Bale cross in the 27th minute and Spurs dominated with Michael Dawson crashing a long-range shot wide and Crouch and Tom Huddlestone both hitting the woodwork.
Kranjcar converted a Kyle Walker cross after 40 minutes and things got worse for doomed Pompey in the second half with both Hermann Hreidarsson and Danny Webber stretchered off.
Gianfranco Zola's West Ham sunk deeper into the relegation mire after a dismal 1-0 home defeat to Stoke and their cause was not helped by fellow strugglers Hull's 2-0 win over Fulham.
Zola's difficult week ended on a new low note with Ricardo Fuller grabbing the only goal of the game at Upton Park, beating three Hammers defenders before firing the winner in the 69th minute.
Iain Dowie's men are now behind the Hammers on goal difference only after cruising to victory over Fulham with a 16th-minute penalty from Jimmy Bullard and Craig Fagan's 48th-minute header.
Wolves edged closer to safety after hanging on for a goalless draw at home to Everton, for whom Leighton Baines and Leon Osman came close while Ronald Zubar shot just over the crossbar for Mick McCarthy's men.