My thoughts on VK are that while I'm not knocking his effort or work rate, it seems a bit naive to just run yourself into the ground every game at this level. Lots of running does not a good player make. Players at this level should be more thoughtful about picking their moments to do the running, and as we're obviously not playing a high intensity pressing system his running is all on his own so won't accomplish much.
Again, not blaming him, I think it's obviously lack of direction from the manager. You can't just have 11 players on a pitch doing their own thing. If the manager wants people pressing and breaking away at pace, that needs to happen as a team and it obviously isn't Ruud's plan.
If he has an experienced leader playing next to him to shout instructions at him that would help so much, but at the moment he's just left to his own judgement and he's not got the experience at this level to do that.
He's still young and there's lots of room for improvement and I think he has attributes to be a decent full back, but I think he needs a rest and Thomas is good enough to rotate in more often. Would benefit both, and the team.