Aberdeen goalkeeper Dimitar Mitov is ruled out for up to six weeks after sustaining a hamstring injury.

Mitov, 27, was replaced by Ross Doohan, 26, at half-time of Sunday's 1-1 Scottish Premiership draw with Hearts at Tynecastle.

"He has been really good but we have a squad and we have to find solutions and stay positive," said manager Jimmy Thelin.

"Ross came in in the last game and did well and we are confident he is going to do a good job for us."

The Bulgaria international has made 20 appearances since joining Aberdeen from St Johnstone in June, recording seven clean sheets.

Thelin's side host Premiership leaders Celtic on Wednesday (20:00 GMT).

Aberdeen, having played a game more, trail Brendan Rodgers' side by four points.

Left-back Jack MacKenzie is close to a return, but will miss the game against Celtic.