Arsenal climbed back into the Premier League's top four for the first time since December when they won 2-1 at West Bromwich Albion thanks to two goals from Tomas Rosicky despite having defender Per Mertesacker sent off on Saturday.
The victory moved Arsenal on to 56 points, one more than Chelsea, who slipped back to fifth, at least until they play Sunderland at Stamford Bridge on Sunday.
Rosicky, whose season has been disrupted by injury, headed Arsenal ahead after 20 minutes and scored the second from a rebound in the 50th minute.
Mertesacker was sent off for a foul in the penalty area on Shane Long after 71 minutes and James Morrison scored from the spot to set up a nervous finale for the Gunners.
Southampton dented the survival hopes of their former manager Nigel Adkins and his Reading team when they beat them 2-0 in a lunchtime kickoff.
Goals from Jay Rodriguez and Adam Lallana sealed Southampton's victory and Reading stayed bottom of the table, level on 23 points with Queens Park Rangers.
Aston Villa moved out of the relegation zone and improved their chances of staying up with a 3-1 win at Stoke City and Norwich City drew 2-2 with Swansea City at Carrow Road.
Photograph: Darren Staples/Reuters