I think it's unfair to criticise Bernardo's performance at left wing back against Man Utd when March and Lamptey have both had the chance to develop into the role. Lamptey is a class above, he could probably play anywhere but March has taken time to warm up to the role. He has played there more often than Bernardo does and I feel very confident that Bernardo would improve if he got a regular run in the side in the position. It is a very different skillset playing LB to playing LWB because there's more of an attacking intent for a wingback and usually there's a player in front of the LB to support. It was the difference in Schelotto playing RB rather than RWB. When he had the space to run into, the Greyhound was best suited. In fact, I'd go so far as to say that he should have been retained if we wanted to play with wingbacks frequently this season.
Schelotto is a good example - capable of looking very good at times as a wingback, looked very dodgy as a fullback (in my opinion)