As I said, for him to perform, we need Hakan to do that too. Otherwise, he's always marked by 3 defenders. There was a good moment, when Hakan woke up and delivered a long pass to Suso, who was open and then delivered a cross in the box.
4-3-3 also suits him better, because the CM gets involved more and together with the RB they form a triangle.
I would cash Suso in. Milan is frozen in this need of playing with wingers, this is not milan. We play in a 442 with or without trequartista.
If he was more than a player that resolve 1 in every 10 games and could play as striker or trequartista i would call him a 'craque'. But he can play only as a right winger.