His head coach, Sheldon Keefe, had some high praise for him.
Per Mark Masters:
Keefe says 22-year-old d-man Mikko Kokkonen "has been maybe the surprise of camp" for him.
"He's been very, very solid all the way through. You look at where he was last year to now, it's been remarkable ... he's kind of been under the radar, but every day he's been very solid."
If Kokkonen continues to work hard, don't be surprised if he earns his spot with the Maple Leafs this year or next.
With the current injuries in the defensive unit, Kokkonen might get a chance sooner than later.