Arsenal ended a run of four Premier League games without victory as they won 2-0 at Bournemouth to go level on points with second placed Tottenham.
Mesut Ozil and Alex Oxlade-Chamberlain scored the goals midway through the first half to move Arsenal above Manchester City to third, behind Spurs on goal difference.
They trail leaders Leicester City by five points with 13 games to play.
Manchester United remain fifth, six points off a Champions League place, after a 1-1 draw at champions Chelsea in this morning's other match.
Ozil put Arsenal in front after 23 minutes with an athletic, right-foot volley after a good header back by Olivier Giroud.
One minute later, Oxlade-Chamberlain rifled a low shot across the goal which went in off the post.
"We beat a good side, it was three difficult points but three very important points for us because we had not won for a while," Arsenal manager Arsene Wenger said.
"We had a strong start, with good finishing and we controlled the game.
"We lost a bit of our urgency in the second half. We lost the killer instinct to get the third goal and on top of that Bournemouth are physically a strong team."
Bournemouth enjoyed plenty of possession and Arsenal goalkeeper Petr Cech had to be alert to prevent the hosts from getting back into the match.
Bournemouth remain 15th, just five points above the bottom three.
United must have thought they had won at Stamford Bridge when they led 1-0 going into injury time thanks to a brilliant second-half goal by Jesse Lingard.
Lingard's tight swivel and unstoppable shot was worthy of winning any game but Chelsea equalised in time added on through Diego Costa.
Spain forward Costa then almost won it for the home side with a fine strike from close range, but David De Gea blocked the shot.
Thibaut Courtois also had a good game in the Chelsea goal as the points were shared.
Chelsea remain in the bottom half, in 13th place.