Sanchez is definitely a player we should give more time to settle, he showed it in the premier league for few seasons already, he can be a top level player. Our football might be different to Arsenal's but I believe with full preseason, fresh start and a couple of other additions he should get back to his best. I am however slightly concerned about his position. He lost quite a lot of pace, while still remained the acceleration. Imo we should play him in the middle. His workrate is high, he can play as a second striker when needed, and when defending he can help too with pressing and winning the ball back, he's a bit too slow for a winger or in case we field 3 midfielders we need at leas one winger to have pace, which means we need inevitably buy a RW because as Jose showed, he's not gonna play Sanchez there..
But give him time, in a dull finish to the season like Mourinho often has when nothing to be played about, it is clear we won't see anything exciting from any of our players..