The England international has been struggling with an ankle problem recently and was subbed off during Sunday's 2-2 draw at Bolton but Phelan says he should be right for Wednesday.
"Wayne Rooney had a bit of a knock," said Phelan.
"He has a little issue with his ankle. We don't know how serious.
"We will have a look in the morning but we think he will be OK for Wednesday.
"He has been playing with it for a couple of weeks now and during the game we decided he wasn't getting into the areas we wanted and he wasn't getting chances, so we had to change it."