Bruce acknowledges the importance of Gayle and his admiration for the player.
He said to reporters about Gayle's fitness: "On the last day in China we thought he was going to be OK. Then he had a setback.
"I hope he can get fit again.
"When I analysed the squad I know he's capable of scoring a goal.
"If you are a Championship manager you'd take Dwight Gayle because he's the best striker in the Championship.
"He must be able to contribute to the Premier League too.
"I hope he will be back before Andy Carroll (September)."