Chelsea suffered another case of the Stamford Bridge stutters as they threw away a two-goal lead to Southampton.
But Rickie Lambert pulled Southampton back into the game with a header three minutes after being sent on and Jason Puncheon then equalised with a brilliant volley.
Jack Wilshere fired Arsenal into the fourth round of the FA Cup with a superb late winner against Swansea at the Emirates Stadium.
The England midfielder - out for more than a year with ankle and knee injuries before returning to action this season - capped a man-of-the-match display to finally beat inspired Swansea goalkeeper Michel Vorm with a 20-yard strike on 86 minutes to set up a trip to Brighton and keep alive hopes of Arsenal's first trophy since 2005.
The Gunners were much improved from the lacklustre 2-0 Premier League defeat to Manchester City on Sunday and, but for a combination of poor finishing and brilliant defending, would have had their cup replay wrapped up well before Wilshere's fine late effort.
Wayne Rooney marked his first Manchester United appearance since December 23 with the only goal of the game as they beat West Ham 1-0 in their FA Cup third round replay at Old Trafford.
Victory saw Premier League leaders United, the record 11-times FA Cup winners, into a fourth round tie at home to fellow top flight side Fulham.
Rooney opened the scoring in the ninth minute after Anderson produced a superb, defence-splitting pass which set Javier Hernandez through on goal before unselfishly squaring the ball to the England striker, who was never going to miss from a few yards out.
The forward could have put the result in this all-Premier League clash beyond doubt in the second half but Rooney blasted over the top from the penalty spot after Jordan Spence handled a cross from Ryan Giggs.