LONDON — The eagerly awaited FA Cup fifth-round clash between England’s two top teams turned out to be a one-sided affair yesterday as Manchester United thumped 10-man Arsenal 4-0 at Old Trafford.

United were 3-0 up after 38 minutes through Wayne Rooney, Darren Fletcher and Nani as Arsenal’s injury-hit side looked badly off the pace and short of motivation.

United, also without some leading players, were just as dominant after the break and Arsenal suffered a further setback five minutes after the restart when Emmanuel Eboue was sent off for a wild challenge on Patrice Evra.

Both teams then made substitutions to rest players for midweek Champions League games but United remained on top and got the fourth with another Fletcher header after 74 minutes.

Humble Barnsley produced an FA Cup sensation when they came from behind to beat Liverpool 2-1 with virtually the last kick of the game to advance to the last eight in dramatic style.

Brian Howard’s 25-yard strike, moments after the Yorkshire club had had a penalty appeal turned down at Liverpool’s Anfield home, sealed a memorable victory for the Championship side and added to the pressure on under-fire Reds boss Rafael Benitez, who controversially made a raft of changes to his side.

It was anything but the result Liverpool, who twice fell behind at Anfield to non-league Havant and Waterlooville in the last round, wanted ahead of Tuesday’s Champions League clash with Italian giants Inter Milan.

In the day’s other fifth round ties, holders Chelsea beat Huddersfield 2-1 while League One Bristol Rovers were the lowest-ranked team left in the Cup after a 1-0 win at home to Championship side Southampton saw them into the quarterfinals for the first time in 50 years.

Also through to tomorrow’s quarterfinal draw were Cardiff City who beat fellow Championship side Wolves 2-0.

In the day’s other all Championship fifth round clash West Browmich Albion beat 10-man Coventry City 5-0.

Liverpool, the five-time European champions, didn’t go ahead until the 32nd minute when striker Dirk Kuyt poked in a cross from fellow Dutchman Ryan Babel.

But Barnsley were level before the hour mark when Stephen Foster headed in a cross from Martin Devaney.

Australia’s Harry Kewell almost wrapped up the tie for Liverpool when his shot hit the crossbar.

Meanwhile, keeper Luke Steele, on loan from West Brom, had a Barnsley debut to remember with several fine saves before Howard struck.

Frank Lampard put Chelsea ahead at Stamford Bridge with a low shot from 18 yards in the 18th minute — the England midfielder’s 100th goal for the Blues.

But Huddersfield, who knocked out Premier League Birmingham in the third round, then shocked the crowd just moments before half-time when Michael Collins struck from 12 yards after a pass from James Berrett.

Lampard then settled Chelsea’s nerves in the 60th minute when, after his shot was blocked by Huddersfield keeper Matt Glenon, he followed up to score from the rebound.

The result was put beyond doubt when Salomon Kalou’s shot went in off Glennon 20 minutes from time.

Rickie Lambert’s deflected free-kick six minutes from time sealed Bristol Rovers’ second notable success of this season’s FA Cup after the team 13th in English football’s third tier had knocked out Premier League Fulham on penalties in the third round.

West Brom went ahead against Midlands rivals Coventry through Chris Brunt’s 12th minute header. Things got worse for the Sky Blues when Michael Doyle was unluckily sent-off for a challenge on Zoltan Gera.

Then a mistake from Coventry goalkeeper Andy Marshall allowed Roman Bednar to double the Baggies’ lead in the 59th minute before the Czech, on loan from Hearts, made it 3-0 from the penalty spot.

And two goals in as many minutes from Ishmael Miller and Gera compounded managerless Coventry’s woes.

Cardiff, the only non-English club to win the FA Cup, needed just two minutes to take the lead at Ninian Park when Peter Whittingham fired home after being played in by Jimmy Floyd Hasselbaink.

The much-traveled former Chelsea striker then doubled the Welsh side’s lead nine minutes later after Whittingham turned provider.

Premier League Portsmouth, a contender to break the 13-year monopoly of the Cup enjoyed by the ‘Big Four’ of Arsenal, Manchester United, Chelsea and Liverpool, are away to struggling Championship side Preston today.

Also in action Sunday are top-flight Middlesbrough, away to Shefield United. The match will be Kevin Blackwell’s first match as manager of the mid-table Championship club after he replaced Bryan Robson this week.