Hajime Moriyasu believes the Albion winger is not facing a lengthy absence after going off against Arsenal.
Mitoma hurt his left ankle during the first half of the 1-0 defeat and eventually made way for Yankuba Minteh at half-time.
An ankle injury ruled Mitoma out for several weeks earlier this season.
Moriyasu was asked for the latest by Japanese media during a domestic club match on Saturday, with the emphasis on whether he will be fit for national team action.
He said: “According to the medical report, he will be able to make it in time for the international break and will not be out for a long time.
“However, depending on the condition of the injury at the time, there are times when he can return quickly and times when it takes longer, so we have to monitor his progress.”
Japan play England and Scotland in the next international break at the end of this month.
Albion have two Premier League fixtures before then, away to Sunderland and at home to Liverpool.
Head coach Fabian Hurzeler has spoken in the past about the Japanese FA’s professional approach with players who have injury concerns.
If necessary, there is likely to be close communication between Albion and Japan over Mitoma’s condition.
Speaking after the Arsenal game, Hurzeler said: “He couldn’t continue the game, so that was disappointing for us because I think he showed a good performance in the first half.
“Now we have to wait for the scan and then we can say more.
“But we don’t think that it’s a big injury.”
AloJapan.com