How slow is Fernandez?
He's not quick, but I hadn't noticed him being worryingly slow or anything.
I've really liked what I've seen of him this season, in both the U18's and U23's. Like Hugill he quickly got promoted to the U23's and I think he's performed well at that level so far, especially given his age compared to some opponents.
As others have pointed out, he's better going forward than defending at the moment. But so are most modern full backs. Especially at a young age before they've learned the tactical, positional side of the game.
He has a lot of positive attributes with his height, strength, mobility and very impressive technique on the ball. I love watching his gliding runs forward that remind me of Javier Zanetti at times - my favourite ever non-United defender. His lack of great pace is maybe his biggest weakness, but I've seen slower players make it to the top.
I can see what people mean about his versatility, and potentially playing as a centre back or even midfielder with his height, strength and technique. But I like what I've seen of him as an attacking left back so I hope he mainly focuses on developing that part of his game first and foremost.