What are their contract situations?
McGregor - who has been linked with a move to the East Midlands of late by other publications - has three years to run on his contract, so Celtic would be in a strong position were Brendan Rodgers to come calling.
Ajer, meanwhile, is also thought to be a target for Newcastle United and his contractual situation is slightly more pressing. Indeed, his deal expires in the summer of 2022, so the club would need to make a decision about his future soon.
What did Neil Lennon say about them?
With former manager Neil Lennon admitting some players didn't want to be at the club even before the season truly started, it's easy to see why some of their bigger names would be linked away when also keeping in mind how things have gone.
While he didn't name names, he had previously suggested back in 2019 that the club would be looking to 'settle' McGregor 'down' after an 'approach' from the Foxes.
In September 2020, Lennon revealed he'd had a heart-to-heart discussion with Ajer after interest from AC Milan.
"You can't control speculation," he said.
"Like I've said, as always, there's been no concrete offers, no confirmation of anything and we don't want to sell him.
"And he's in a good place mentally.
"I've spoken to him on it yesterday and I'm there as a support for him.
"Sometimes it can be a very distracting situation, which he finds himself in.
"So he's getting all the support he can from myself and the backroom team, as well as his team-mates."
Should Celtic look to sell?
In the case of Ajer, it may be wise to consider his expiring contract. Amid reports of Celtic looking for a major overhaul this summer, trying to get any sort of fee for him while they can may potentially help fund new additions.
With McGregor, those behind the scenes do have the security of a relatively long-term contract. Unless there's a bid they cannot refuse, it would appear as if they do not need to sell him.News Now - Sport News