The ex-Reds defender has followed his fellow Norwegian's progress carefully and feels the midfielder has an exciting future ahead of him.
Daehli is looking to make the step up from Academy football next season into Warren Joyce's Under-21 squad after scoring on his sole appearance for the Reserves last term.
"Mats is an amazing talent," declared Johnsen to ManUtd.com. "It's going to be fun to watch him develop.
"He is still very young but is a player that Norway needs to come through now. Hopefully, he is going to get there and it will go the right way for him as the future looks bright.
"Of course, he is in the right place and it's very nice for him. He's young but has a proper mentality for the game as well so he is going to somebody who is worth watching."