Romelu Lukaku and Timo Werner were substituted with injuries midway through the first half of Chelsea's Champions League clash with Malmo on Wednesday.
The duo left the field with Chelsea two to the good following goals from Andreas Christensen and Jorginho.
Lukaku was injured in the process of earning the Blues a penalty, bulldozing his way through the Malmo defence and being hacked down by Lasse Nielsen when through on goal.
He tried to return to action following lengthy treatment from the challenge on his ankle, but soon signalled to the bench that he was in need of substituting and was replaced by Kai Havertz.
Werner was brought off with a similar problem just before the break, with Callum Hudson-Odoi coming on.
"It is difficult to judge whether he needs a break or is it better to keep him on the pitch," Tuchel said.
"At this moment, I feel Romelu is a bit overplayed. I think he played in too many competitions over the summer, too many competitions with his country. He played the Nations League and he is a fantastic athlete and such a competitive guy that he never takes it easy.
"He wants to be out there and win. He wanted to have a good outcome for the European Championship with Belgium and now in the Nations League it was a huge match for him, it meant a lot personally to play for his country so he takes it seriously.
"If that does not work well he always puts it on his shoulders. He reflects about it and I feel him [being] mentally tired."