The Belgium attacker was a second-half substitute for the 4-2 win.
Pioli said, "He is a smart guy, he can read some situations in advance, he had a strange summer so he still isn't in his best shape.
“There are no doubts about his talent, but he has joined the club from a different league and he'll need time to adapt.
“We already are in good shape, we have intensity and the players like to play this way. If we run well we can dominate games and feel better than our opponents."