The Japanese international has struggled to force his way into David Moyes's plans this season and was replaced at half time by Adnan Januzaj during yesterday's 2-1 loss to West Bromwich Albion at Old Trafford.
"I just decided I wanted to make a change," Moyes said of the playmaker after the defeat. "We want Shinji to feel he has an opportunity to show what he can do.
"His best position is arguably at number 10 playing behind a main striker, but he's used to playing on the left-hand side with Japan.
"There is a lot of competition here and we want to push each other to improve performances."
It has resulted in speculation that the 24-year-old could depart Old Trafford in the near future, with his former club Borussia Dortmund and Atletico Madrid believed to be monitoring his situation.
Kagawa scored six goals in 30 appearances during his debut campaign with the Red Devils last term.