Was Tkachuk playing hurt? Don't know if the source is reliable, but this is the first I've heard of it.
https://twitter.com/user/status/1417540936544907268
I also remember Treliving saying in his end-of-season presser that Tkachuk didn't skate a lot last offseason. Add in all the speculation about the Muzzin incident and I don't know what to believe as to why he seemed off.