The winger has been pulled out of international action and was rated 50-50 to face Crystal Palace as Fabian Hurzeler spoke to media on Thursday morning.
Albion head to Selhurst Park tomorrow (2pm) and an appearance for Mitoma, who has an ankle issue, would be his first for five weeks.
He will not be part of Kirin Cup fixtures with his country against Ghana and Bolivia, both in Tokyo.
Albion boss Hurzeler said: “We are always in touch, especially my medical team.
“It’s always important to understand what the player needs, what’s important for the player, how he’s able to handle a lot of games in a short time period.
“Mitoma is a big player for us. We have to make a rational decision for sure.
“We want to have the best players available as quick as possible, but the key thing is really to make rational decisions and therefore, it’s very important to work with the national teams, to give them an understanding where the player is, how we see the player, what makes sense for the player to do in an international break.
“Is it to travel to his country and play their two games in a short period?
“Is it to continue doing work on the training pitch, to be ready for after the international break.
“It’s always a very important exchange we need to have.
“With the Japanese national team, we have an ongoing exchange and it’s very professional how we handle it.”
Diego Gomez could be handed a left-of-centre role at Crystal Palace after his two goals against Leeds last Saturday.
AloJapan.com