Aberdeen boss Derek McInnes has confirmed Joe Lewis suffered cartilage damage in the 2-0 defeat to Rangers which leaves the goalkeeper requiring a "significant operation" on his knee.

Lewis was stretchered off after clashing with Josh Windass as the attacker advanced on goal, with Rangers winning a penalty through the incident.

The Dons initially feared the stopper had broken his leg. While there was relief when it was discovered that wasn't the case, MRI scans confirmed Lewis suffered significant knee cartilage damage at Ibrox.

"Good news and bad news," said McInnes. "He hasn't broken his leg, which initially was the big fear.

"But once he'd been to the hospital for the MRI scan last night it became clear Joe will need an operation on his knee.

"He's got cartilage damage and will need a significant operation on his knee which will rule him out for the foreseeable future."

With Lewis set for a lengthy period on the sidelines, McInnes says the Dons will now attempt to find a replacement.

However, first he is looking to give youngster Danny Rodgers a chance to claim the jersey this weekend.

Asked about whether he would look to find cover, he said: "That's what we will try and do.

"We will look at all our options, we've got young Danny who has got good experience in the championship the last couple of seasons.

"He'd had the benefit of working alongside Joe and will get an opportunity tomorrow."

Aberdeen confirmed the signing of Hamilton defender Mikey Devlin on Friday.

McInnes believes he has snapped up a potential star at a cut-price due to his recent injury record.

"Very pleased," he said. "Obviously, we spoke with Mikey a few weeks ago and made a pitch.

"It was more for next season obviously, it's not a position we see as a priority for now but we managed to find an agreement with Hamilton to get him up with us.

"He will now continue his rehab with us and hopefully we will see him in a red shirt before the end of the season.

"To get the Hamilton captain, someone we have always been attracted to, someone with a good size and at a good age.

"Yes, injuries are part and parcel of the game and he's to overcome that but I think he will be a brilliant signing.

"If he hadn't had that injury he'd likely of moved for big money down south.

"We think he has the best years ahead of him."

McInnes also confirmed the Pittodrie board have knocked back a third bid for centre-half Scott McKenna, before reiterating the defender will not leave the north-east during this window.