This season, yes. But Sanchez has mentally checked out. We can't judge him on this campaign when he doesn't want to be there. He's playing in a far worse team than Sané too, and if Sanchez played brilliantly this season, got them to the top 3 in the league and won them the Community Shield, what would be the chances of Arsenal letting him go in January? Close to zero, I'd imagine, and that's probably playing on his mind.
Sané's last run of really good performances ended away at West Brom when he scored the opener. Since then he's occasionally popped up with goals and assists (Tottenham and Burnley games) but has been off it on the whole.