With Auba out left, he's forced to come back and help. When he's at the 9, he's to much of a goal scorer. Lacazette, fo the personell we have in midfield, works back naturally, which is what is needed
Laca plays almost as a False 9 sometimes which works when you have blistering wingers like Saka and Auba. I think we would see alot more from Auba with a true #10. He's not really that great in the air, so you gotta give him the ball to feet or put it over him and let him run on to it. There's no players in the side right now with that sort of skill set.....besides Ozil..