LONDON - Premier League sides Manchester United and Aston Villa reached the fourth round of the FA Cup on Sunday after seeing off lower league opponents Southampton and Gillingham. United beat Championship strugglers Southampton, who played for almost an hour with 10 men, 3-0 at St Mary's Stadium and will now meet Tottenham Hotspur at Old Trafford in the fourth round. Aston Villa won 2-1 at League Two Gillingham with James Milner celebrating his 23rd birthday by scoring both goals. Villa will travel to play the winners of the postponed tie between Cheltenham Town and Doncaster Rovers in the fourth round in three weeks' time. United, who were last beaten in the third round of the FA Cup 25 years ago, weathered some early pressure from Southampton but the outcome was rarely in doubt after Danny Welbeck headed home from two metres out in the 20th minute. Southampton were in more trouble 16 minutes later when teenage defender Matthew Paterson was sent off by referee Mike Riley for a studs-up challenge on United defender Nemanja Vidic although the challenge hardly troubled the Serbia defender. United effectively wrapped the tie up in the 48th minute after Riley made another controversial decision, ruling that David McGoldrick had handled a Nani freekick when the ball appeared to hit his back. Nani duly converted the penalty. Substitute Darron Gibson scored United's third after 81 minutes. YOUTHFUL EXUBERANCE Manchester United manager Alex Ferguson told Setanta Sports TV afterwards he expected to win the game against a young Southampton side. "We could have done it more comfortably but 3-0 is a satisfactory score," he said, adding that he thought Paterson's sending off was down to youthful exuberance rather than anything malicious. "I think if the referee had booked him in the first minute it might have calmed him down a bit. It was exuberance more than than anything else. He was charging about a bit and tackling, all the things you expect from a young player and he was a bit over-enthusiastic maybe." Villa were made to work hard for their victory at Gillingham, who won the praises of Villa manager Martin O'Neill. "Never for one minute did I feel comfortable. Gillingham were always in the game even when we were leading 1-0." Milner put the visitors ahead with a superb strike after 13 minutes after playing a clever one-two with Stilian Petrov, but Gillingham's endeavour paid off after 57 minutes when they equalised through Canadian international Simeon Jackson who blasted an unstoppable shot past Brad Friedel. Villa though, regained the lead with 11 minutes to play when Milner scored from a penalty after Gills skipper Adam Miller was adjudged by referee Keith Stroud to have brought down Ashley Young.