Beleaguered Manchester United manager David Moyes admits he urgently needs to buy players in the January transfer window but confesses it may not be possible.

The Scotsman was talking in the wake of another major disappointment for United as the record 11-time winners of the FA Cup were knocked out at home in the third round by Swansea.

The 2-1 defeat marked United's fourth home loss in their last six games at Old Trafford and just the second time in 29 years the club has been knocked out in the third round of the competition.

Moyes only brought in Marouane Fellaini, from his former club Everton, after taking over at Old Trafford in the summer and with every growing setback, pressure is mounting on him to improve a squad that is looking well beyond par and which was without seven injured first team players on Sunday.

"I said I would try but probably would be doubtful in January because of the window but I think I have been saying it fairly consistently," said Moyes.

"There is an urgency that we would like to bring people in but are those players available in January?

"So there is no point in me hyping it up because the players we would like to bring in are probably not available in January."

Swansea capitalized on the 80th-minute sending-off of substitute Fabio Da Silva by scoring in the last minute through Wilfried Bony.

Meanwhile, Chelsea and Liverpool advanced relatively comfortably.

Chelsea and Liverpool played stronger lineups — and it showed. Second-half goals by John Obi Mikel and Oscar earned Chelsea a 2-0 victory at Derby. Liverpool avenged last season's defeat to third-tier Oldham in this competition by winning 2-0 at Anfield thanks to Iago Aspas' first goal for the club and an own goal by James Tarkowski.

The game also saw Liverpool manager Brendan Rodgers face his son, Anton, who plays for Oldham and came on as a substitute.

"I've seen Anton's life from when he was a young footballer and to see him run out there was a bit surreal really," Rodgers said.