Sandro has always been less talented, but more clinical finisher compared to Munir, who is more versatile, technically gifted, but then less of a finisher.
What failed him in his last season here was loss of quality in his most strongest asset - finishing.
IN 2014/15, his breakout season, he was quite good for first team whenever he had a chance. He scored 4 goals for first team, goal per 65,2 minutes, which is a very good result, getting total 261 minutes, not much.
He got 4 more times minutes last season, but only managed to produce 3 goals, all in copa del rey (compared to scoring even in CL a season before). He clearly lost his mojo.
Now he is scoring at rate of 120 minutes per goal, in struggling Malaga side, that is a great result.
Sandro will never be a world-beater, but he can definitely be a mid-tier La Liga forward, scoring around 15-20 goals per season, someone like lets say Soldado used to be, no nonsense central forward.
He has speed and with gametime he has obviously regained his finishing ability.