Deila signed his fellow Norwegian back in February but the 18-year-old midfielder stayed with IK Start until June, when he joined up with his new club.
Of course, Ajer will never play under the 42-year-old, who failed to earn a contract extension at Parkhead as Rodgers replaced him earlier this summer.
Rodgers spent over three years as Liverpool manager before taking over in Glasgow, with the Northern Irishman aiding the development of a certain Raheem Sterling, who perhaps has not played his best football since parting company with his old manager and Liverpool last summer.
He also nurtured a number of young talent during his spell at Swansea City, and Deila is convinced that Ajer is in safe hands despite his exit.
"He is a mature young player and Brendan Rodgers is very good with young players," he told Norwegian newspaper VG, quoted by STV.
"Being managed by a fellow Norwegian when playing abroad is not the easiest thing so I don't think it's a disadvantage for him that I've left the club."
Ajer netted 14 times in 59 outings for the Norwegian side in an impressive run of goalscoring form which indicates he knows precisely where the goal is.