Minamino, Hwang, Mwepu all looked better and this RB system looks like it will produce chances against any side in the world, so complaints about him playing for some poor side are not so justifiable. The age argument is, though.
It's at the back where they are leaking, but you can see (while they had energy) they were threatening all the time even against this Liverpool side. Hard and pretty much impossible to guess how he will handle transition to different style of play and will it be too soon for him.