Nani and Darron Gibson effectively wrapped up the contest during a first half in which Cristiano Ronaldo controversially had a goal ruled out for offside.
Ronaldo did eventually notch his 15th of the season, with Danny Welbeck rounding off the scoring after Miles Addison had headed home Derby’s sole consolation.
Everton reached the quarter-finals for the first time since 2002 after turning over Barclays Premier League rivals Aston Villa 3-1.
Jack Rodwell fired Everton into an early lead before Villa ace James Milner equalised from the spot, all in the first eight minutes.
Then Mikel Arteta’s penalty reclaimed the lead before the break, with Tim Cahill getting the clincher with 14 minutes left.
Swansea and Fulham must play each other again for a place in the FA Cup quarter-finals following a pulsating draw at the Liberty Stadium. Swansea dominated the first half but went in at the break a goal behind following captain Garry Monk’s unlucky own goal. But top scorer Jason Scotland restored parity seven minutes into the second half to force a Craven Cottage replay.
Blackburn Rovers defender Christopher Samba grabbed a dramatic equaliser in stoppage time to secure a replay in their FA Cup match with Coventry City. Samba took advantage when stand-in goalkeeper Andy Marshall spilled substitute Keith Treacy’s effort. It was tough luck on Coventry who had forged ahead through Aron Gunnarsson and Michael Doyle after Roque Santa Cruz had opened the scoring.
Kevin Blackwell saw his Sheffield United side hold Hull City to claim a place in the FA Cup quarter-final draw. Greg Halford put the Coca-Cola Championship side ahead with an early header in the fifth-round tie at Bramall Lane but Barclays Premier League team Hull responded to force a replay. Kamil Zayatte, pushed into midfield from defence, claimed the equaliser with a strong header before the interval.
West Ham full-back Herita Ilunga headed a late equaliser against Middlesbrough at Upton Park to earn a replay from their FA Cup fifth-round tie. Boro had led through Stewart Downing’s first goal of the season and Gareth Southgate’s men looked good value for their lead until Ilunga struck. The Congo defender has a taste for the cup – both his goals this campaign have come in the competition and it keeps alive Gianfranco Zola’s hopes of winning the trophy as a manager.
In the day’s late kick-off Nicolas Anelka struck a superb hat-trick to put Chelsea into the FA Cup quarter-finals and ruin Watford’s hopes of a giantkilling act. The Hornets had stung Chelsea in the 69th minute when substitute Tamas Priskin raced clear to give the home side the lead. But Anelka equalised in the 75th minute and put Chelsea in front with a header two minutes later. The France striker finished off Watford with his 20th goal of the season in added time.
Fifth Round Results
Swansea City 1-1 Fulham
Blackburn Rovers 2-2 Coventry City
Sheffield United 1-1 Hull City
West Ham United 1-1 Middlesbrough
Watford 1-3 Chelsea
Everton 3-1 Aston Villa
Derby County 1-4 Manchester United
*Arsenal are due to play their FA Cup fourth round replay against Cardiff City on Monday night. The winners will face Burnley in the fifth round.
Replay matches are due to take place in the week commencing 23rd February.
Sixth Round Draw
Blackburn Rovers or Coventry City v Chelsea
Swansea City or Fulham v Manchester United
Cardiff City or Arsenal or Burnley v Sheffield United or Hull City
Everton v West Ham United or Middlesbrough
Ties to be played on 7th/8th March.