Farsley had defender James Knowles sent off and saw Oxford awarded two disputed penalties at the Kassam Stadium.

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Deacey said: "It was a day to forget. And that's what we need to do...forget about this and now concentrate on the last four games.

"We didn't defend very well in the first half and that gave us an uphill task. We got back into it at the start of the second half but then some of the decisions that went against us were a disgrace.

"We've got to regroup and go again this week."

Celtic's relegation fears increased as, just a week after winning at Torquay, Deacey's men crashed to one of their heaviest defeats of the campaign and had Knowles sent off at the start of the second half.

It seemed a harsh red card with Knowles doing little more than shoulder-charging Oxford striker Yemi Odubade as he ran towards goal. But referee Ian Cooper awarded a spot-kick and dismissed the player.

Goalkeeper Curtis Aspden superbly saved Adam Murray's penalty, but it just wasn't Farsley's day as they conceded another later in the half.

Oxford took the lead after just three minutes when Barry Quinn's long ball was flicked on by Craig McAllister and Odubade sprinted past Georges Santos and Scott McNiven before finishing neatly.

They then hit the woodwork twice in five minutes. Phil Trainer struck a 22-yard free-kick against the left post before Craig McAllister headed Eddie Anaclet's right-wing cross against the upright when it seemed easier to score.

And five minutes before half-time it was 2-0.

Odubade was brought down on the edge of the area by Stephen Downes, and
Trainer drilled home the free-kick.

Celtic replaced Steve Torpey with Simon Bambrook for the second half,
and he scored with his first touch. Farsley won a free-kick on the edge of the box and Bambrook shot low through the wall and past Billy Turley.
But two minutes later came Knowles' dismissal, and with 10 men it was always going to be tough for Farsley.

Oxford sub Matt Green converted Michael Howard's low centre from the left to put them 3-1 ahead and the contest was effectively over when Odubade won a penalty for the second time with 10 minutes to go when Santos brought him down.

Murray had the confidence to go up again, and this time went the other way – and scored.

Green completed the rout with a composed finish in the final minute when goalkeeper Aspden was way out of his goal.

OXFORD UNITED: Turley, Day, Quinn, Foster, Howard, Anaclet, Hutchinson, Murray, Trainer (Rose 66), McAllister (Green 60), Odubade (Richards 88). Subs not used: Clarke, Hand.

FARSLEY CELTIC: Aspden, Downes, Torpey (Bambrook), Santos, S McNiven, Watson (Heath 83), Knowles, Krief, Prendegast, D McNiven, Reeves (Tuck 75). Subs not used: Stamer, Backhouse.

Referee: Ian Cooper (Kent).