Felix needs to play regularly to bring back his work off and on the ball again. He looked so lazy af when he played, and i think Conceição can pressure him. His team lost against Feyenoord, but it seems he's improved by seeing his game play. He only having very low work rate work on and off the ball.
That's what he needs to get because so far he lost his place in the first team when he was at Chelsea which affected his performance and his game performance. At Milan itself there hasn't been a big change that he has made because maybe he still needs to adapt first but if he plays regularly then I'm sure he will continue to improve. Conceição can give him more tasks considering that during the match Felix didn't show good performance and the defeat to Feyenoord could have been avoided if his team played better.