As a Turkish person I might be a little biased towards the whole Arda Guler situation, but I have to say the kid is only 18 years old and from the images that we have seen so far, from the day he got to the team versus the latest pictures that we got of him, we can clearly see that he has put on some serious amount of muscle on his legs, not that huge of a difference on his body but his legs definitely got huge compared to how it was just six months ago. That could be one of the reasons why he got injured so frequently, they know that he is talented, but they are overloading him with extensive training that pushes his body to limits which injures him a lot. The moment they let go of his training situation, he will probably get better and won't get injured as much.
I agree with your opinion that A player must train his muscles to minimize the threat of injury because strong muscles will make The bones stronger. This is because The muscles are often trained to be in sync with The bones so that the bones are able to maintain balance when The foot is on The wrong foot.
For Arda Guler, it would be A good idea to rest first so that Ancelotti doesnt play until he recovers optimally in order to minimize A more serious injury that will darken Arda Guler future.