The attention of the club will revert from their league campaign to knockout football this evening with a place in the second round of the FA Cup at stake, but the strain of a League One derby with Huddersfield Town is threatening to weigh on Leeds tonight.

United have had little more than 48 hours to recover from Saturday's
2-1 defeat to Huddersfield and reorganise themselves for an FA Cup first-round replay at Sixfields, and manager Gary McAllister admitted signs of fatigue were appearing among his players for the first time.

McAllister would prefer to avoid wholesale changes for a televised match which Leeds have a strong incentive to win, but a number of alterations may be unavoidable after Saturday's intensive derby.

Leeds fielded an unchanged line-up at Elland Road after running Derby County close in round four of the Carling Cup last Tuesday, but McAllister admitted a number of his substitutions against Huddersfield were made earlier than planned as a result of increasingly tired legs.

Jermaine Beckford was introduced after 63 minutes and Jonathan Douglas and Fabian Delph were withdrawn with 14 minutes to play, the latter at the end of what could be the first of three appearances in four days, culminating in a possible outing with England's Under-21s tomorrow.

The physical pressure on Northampton's squad is comparable after their 1-0 defeat to Oldham Athletic on Saturday afternoon, however, and McAllister insists his players will not be allowed to forego the chance to reach round two of a competition he won as a player with Liverpool seven years ago – and in which Leeds have not won a match for five seasons.

McAllister said: "We look forward now.

"It's a quick turnaround but we've got a chance to progress in the FA Cup.

"I thought there were little signs against Huddersfield of tired legs so we flipped things round and made some changes earlier than I would have liked.