He's not really a bad defender. It's never been a noted weakness for him in his development, and the idea basically comes from that one nightmare game he had for the senior team, so soon after his debut and having seemingly been made first choice with no settling-in. Neglecting the fact that he was sometimes very good indeed in the handful of games before that one. And he got great reviews at Castilla. Plus without Varela we wouldn't have Rashford. He crossed for Mata's assist for Rash's first goal, and then assisted the next two himself! Without those goals he'd probably be back in the U21s and the world none the wiser.
We have a number of players Mourinho might use at RB, but not many actual RBs. Valencia might seem a more Mourinho-friendly type, but he's hardly a defensive rock himself. And Darmian, while obviously potentially a good player, is surely too delicate for Mou. Varela is a proper RB who has been brought all the way up as a proper RB, and he has real, thoroughbred quality. Could be a Bellerin for us. Imagine him and one side and Shaw on the other, our attack would instantly be so much more multifaceted.
Seems a waste to send him on loan, to me. And I'll be gutted if we sell without him getting another stab at taking the position.