The midfielder is set to join the Scottish Premiership side in the coming weeks.
The 18-year-old will play his final game for the Norwegian club this weekend before moving to Parkhead after a £750,000 move was agreed.
And Borufsen has not only backed the youngster to feature often under Brendan Rodgers, but to ultimately prove to be a fantastic signing for the Hoops.
"Celtic are a good team but there is no reason why he won't get a game as he is a very good player," he told the Record.
"He's shown here that he can handle everything that has been thrown at him and I am sure he will do well in Scotland.
"People forget he is still only 18 because he has an adult head on his young shoulders.
"He's been given a chance by going to a huge club and will go on to be a big star."
Although Ajer's talent is undeniable, he does face a considerable challenge if he wants to hold down a regular spot in the first-team in the near future.
Rodgers arrives at Celtic Park with arguably too many midfielders to pick from, so adding Ajer to the mix will make his need to get some of the fringe players off the books much more urgent.
However, with Ajer being a Ronny Deila signing, it may well be that it is the prospect that has to prove that he deserves to be a part of the new manager's plans straight away as the Northern Irishman may not hold the same level of optimism about his talent as his predecessor did.
But judging by his teammate's praise, it will not be long before Ajer is proving to his new manager just why he is so highly-rated.