Onana performance was so poor last season, I was thinking the first thing that Manchester United will do is get a new goalkeeper when the transfer window is open, but they didn’t do that, but seriously Manchester United just need to sign a better goalkeeper, I don’t really know if Onana performance is going to improve, they just need replacement for him, they shouldn’t depend on Onana completely.
Onana should be kept as a United keeper and put on loan so that that when he improves, his value goes up and money can be made off him to balance the books especially that football is a business and also beating the system of financial fair play 
Otherwise, both attack and defense were terrible and needed urgent surgery...but am surprised Onana hasn't been a topic of urgency but with his injury this void has brought the issue into the spot light, lets see how the club handles this after Martinez move failed.