Chelsea put Arsenal under pressure with a 4-1 away win at West Brom to draw level on points with their London rivals at the top of the Premiership.
Arsenal managed a 2-2 home draw with Southampton, thanks to a late strike from substitute Robin van Persie.
Portsmouth pulled off a shock victory against Manchester Utd. David Unsworth opened the scoring with a penalty, with Yakubu getting their second.
Last weekend, Utd ended Arsenal's 49-match unbeaten run in the league.