Sheehan has been given the go-ahead to play again after suffering concussion during last month's 1-1 draw at Yeovil Town and Telfer's groin strain has eased sufficiently to allow him to return to contention for tomorrow's game at Elland Road.

Leeds are chasing their first League One win since the opening day of the season and McAllister is placing equal importance on the production of a clean sheet by his players.

United have recorded only one shut-out from seven matches this term – during the impressive 4-0 victory over Crystal Palace in the Carling Cup – and McAllister admitted his side's lack of defensive solidity was his key worry after a start to the season which has brought five points from four fixtures.

"I'm concerned that we're conceding goals and that's something we've got to put right," he said. "It's got to be a bit more 'over our dead bodies' when we're defending. I'm still looking for people to step forward and make the back four pick itself because with certain goals you can point the finger.

"But it's about the whole team and everybody defending, rather than looking at the back four and the goalkeeper.

"Going forward we're creating chances and we look as if we can score goals and we have been working the opposition goalkeepers.

"Defensively, as a whole unit, we need to be better."

Sheehan was a regular inclusion at left-back until a knock to the head at Huish Park left him needing neurological examinations, while Telfer would have featured in last weekend's 2-2 home draw with Bristol Rovers had he not failed a fitness test shortly before kick-off.

McAllister is unlikely to be able to turn to striker Enoch Showunmi tomorrow, however, after the striker's early exit from Tuesday night's Johnstone's Paint Trophy victory over Bradford City.

Showunmi is carrying a back injury and may not recover in time for the meeting with Crewe, who are travelling to Leeds with a record of one league win and three defeats behind them.

"Enoch's a bit sore and that might take longer to settle," McAllister said.

"But we've been given an absolute green light from the specialist who looked at Alan.

"He's clear and he's available for selection, and he had a run-out in a behind-closed-doors match against Doncaster Rovers on Thursday.

"With Paul (Telfer), I'm very positive there as well."

Tomorrow's fixture will see the return to Elland Road of Anthony

Elding, who parted company with Leeds to join Crewe in July.

The striker was signed by United from Stockport County at the very start of McAllister's reign as manager, but Elding made only nine appearances before being told he was no longer required.

"The timing wasn't the best for him," McAllister admitted. "But I'm not going to make a big thing about Anthony.

"My only concern is Leeds United getting three points, and it's not about anything else.

"I know we're at an early stage of the season, but I wanted more points on the board.

"We had Crewe watched against Macclesfield in the Johnstone's Paint Trophy, and Crewe are what they are. You've got to admire them for their principles and they're a club who traditionally have tried to play good football. They'll stick to those principles.

"For us it's about getting the happy medium between performances and results.

"You don't have to tell me that we're in a results business, but if you can marry the two together then so much the better."