Allardyce missed the 2-0 win at former club Bolton on Sunday and will also miss Wednesday's trip to Fulham in the Premier League.

Tests have revealed that the 55-year-old, who has complained of chest pains in recent weeks, requires an angioplasty, a procedure which involves inserting a stent to widen a narrowed coronary artery.

The operation is scheduled for Friday and means Allardyce will also be absent from Rovers' clash with Stoke at Ewood Park on Saturday, but McDonald is hopeful that he will be fit to return ahead of the Carling Cup quarter-final against Chelsea.

"The procedure is on Friday and they are saying if everything goes according to plan then (he will be back) in the next couple of days," McDonald said.

"We are hoping he will be back for the Monday before the Chelsea game.

"He is a strong man. He does everything as he has to and if this week goes according to plan with another result against Fulham, it will take all the stress out and he will come back quickly.

"When you are talking about the heart and an operation it's always a concern but I think he has been reassured that it is routine."

McDonald has been in close contact with Allardyce and said the win over Bolton - Blackburn's first away league victory this season - had lifted his spirits.

"I'm in touch with him on a regular basis and he's very happy with Sunday's performance and result, and I'm sure he'll be looking for exactly the same on Wednesday," said McDonald.

"I could tell in his voice that he was happy. He didn't watch the game from the start but he did afterwards and he really enjoyed it.

"He thought it was a little bit scrappy in the first half, but he thought we played well second half and thoroughly deserved the victory. That put a big smile on his face because it was against his ex-team."

McDonald insists Allardyce was never in any danger of underestimating the levels of stress in his job.

"In pre-season he was in London getting himself checked out," McDonald added. "He is a person who knows about the stress, he has been in the job for a long time.

"He knows what the stresses and strains are and he looks after his body accordingly.

"That is why he has picked up on what has happened now, and done so early. If he didn't look after himself, the consequences might have been worse."