Herrera I would say is overrated and underrated in equal measure so it cancels out yeah?
Underrated - Valencia
His final ball hasn't even been that bad under LvG, and when he's been fit, he's been one of the best right backs in the league probably (since LvG took over). Just a tank all over the pitch, reliable on the ball, and while he always turns back when he goes too far forward, it's still better then anyone else in our team can manage basically. He is more then deserving of being our starting right back.
Honorable mention to Blind probably, as he's been incredibly consistent this season.
Memphis as well. Not that he's been good, but so many have written him off even though he has talent and is suffering due to a lack of chances/terrible style that we play/lack of quality in our attack meaning if he doesn't do something good to make an impact, we have nobody to fall back on really.
Overrated - Schneiderlin probably. Just not that good, at least not in this system or when he's played. Very good defensively speaking, but useless in possession.
Or Smalling among United fans (though everyone else underrates him). Don't get me wrong, he's a good defender, but I'm not convinced he'll be a really key player or indispensable or ever reach that top level, because he lacks that ability on the ball. I mentioned it in another thread, but playing him and blind at the back is basically using those 2 players as partners because they both lack a major part that the other has. Both like half players, instead of just using 2 complete center backs who can both be dominant in the air or play the ball our the back. As it is, Smalling goes for every single ball in the air and physical tussle, while Blind does everything on the ball. Becomes predictable and can lead to mistakes like against Spurs where Smalling felt he had to run all the way over to where Blind was to compete for a header and left us out of position.