He's a rookie, he's 19 and it's been a LONG off season. Remember these kids have gone from their last game as a college player going right into NBA draft training, into combine and team work outs into summer league. Maybe a small rest, right back into training and getting the body ready for the beating they are going to take.
He looked really good in the last game, he's going to have his ups and downs. A lot is in his head right now. Brown looked Meh his first month or so, then he got better and better. Tatum looked better than Brown did his first summer league, so I'm not too worried about Tatum. Rather him start slow and finish the season strong when we need him most.