But how good he was last season doesn't mean much. He can be better then he was last season but on the other hand he can be worse than he was last season. For example, in my opinion Di Maria a season before he joined us was a top top player, one of the best 3 in the world at the time (just bellow two crazy ones) but he didn't translated this form in United jersey because of many reasons (wrong system, wrong playing position, wrong manager, wrong place, wrong time). On the other hand Martial was talented but not great a season before he joined us but he has had a much much better season at United as he had before even if he had to lead a broken attack. So even if Di Maria was way better then Martial a season before they joined us the one who was better could be described as our biggest flop and the worse one could be described in 5 years like a best deal in a long time (both costed similar amout of money...).
What is important that Micki has all the skills to be great player for us and he is a type of player we need on the RW. But it is up to him and our manager how e will turn out.