United tackle Luiz Felipe Scolari's men in a Premier League blockbuster at Old Trafford on Sunday knowing victory will drag them to within a point of the Blues, with two additional matches in hand.

That obvious incentive will ensure the Red Devils' heads are cleared after their reverse at Pride Park, with Vidic in no doubt United will be ready for battle.

"The Premier League is different," said the Serbia defender.

"We know what it means for both teams and we are looking forward.

"It will be a great game and we will be doing our best to win."

Indeed United's first loss in 15 matches may have come as a direct result of Sunday's game.

Knowing his side had another meeting with Derby in a fortnight to turn the tie around, Vidic wonders if sub-consciously they eased off the pedal last night, keeping something in reserve for an eagerly-awaited confrontation which would leave Chelsea in big trouble if they lost.

"Maybe in the back of our minds we always recognised we would have a second chance," reflected Vidic.

"Maybe that is why we didn't perform as we can and Derby took advantage of the fact we played badly."

No-one from the United camp, least of all Sir Alex Ferguson, begrudged Derby their success.

Watched by new boss Nigel Clough, who takes over officially today, the Rams tore into the Red Devils from the start and, as Ferguson also acknowledged, in the end the visitors were relieved still to have a chance of reaching Wembley on March 1.

He will also take a check on Wayne Rooney, who limped out of one crunching challenge just before the end, and Rio Ferdinand, who has been having extensive treatment on a back injury that has kept him out since United returned from their successful Club World Cup campaign in Tokyo three weeks ago.

Patrice Evra is definitely back after suspension and a run-out for Cristiano Ronaldo last night should have helped the Portugal international in his search for top form.

Amazingly given the 42 goals he scored last season and the explosive manner in which he returned from a summer ankle operation, apart from a lone strike against Gamba Osaka in Yokohama, Ronaldo has not found the net in competitive action since November 15.

Sunday would be a perfect time to end that barren run, with Vidic putting Derby on the back-burner until they head to Old Trafford in a fortnight.

"The second match will be different," he warned.

"They will probably come to defend and try to survive.

"It's going to be a big match because we want to get to Wembley and win the trophy."