Same as you would any other coach/manager. Is he getting the best out of the players at his disposal, performing at least as well as can be expected in the league/cup competitions, showing signs of improvement and progression along the way?
I may be wrong and there are plenty more qualified and knowledgeable than me to make that call, but in my humble opinion, I’m sure we could and should be doing better and if that means a change then so be it.
Underachieving isn’t accepted at senior level so why should complacency be allowed in the youth set up?