Will Arda Guler follow in Hazard footsteps at Real Madrid, who continues to suffer from injuries, so to date he has not made his debut after being recruited from Fenerbahce. After playing several matches on the pre-season tour yesterday, many said that the Turkish player had qualities like Mesut Ozil.
I mean it is just the start of his career so we do not really know how it will go, there is really no reason to assume the worse just yet, it has been only a few months since he got there. Plus, he doesn't have any serious injuries so far, just small time stuff and he is not ready to play just yet neither, his skills are great but his body can't handle all the overload that a team like Real Madrid has. Remember, this kid didn't play all that many games so far, and they got him on a future potential thing and not what he has shown all season long, he didn't had a single 30+ game season so far.
I think they are just bulking him a bit and putting some small amount of muscle into him, so that he could do great. You do not have to be buffed, but you need to be at least core strength just like how Modric has, he may not be all that muscled ripped body, but he is strong on his foot and that is something Guler is missing. It may take time and he may get injured multiple more times while growing to be like that.