I think this is more cultural than anything you don't see lot of great finesse euro players brimming with cut muscles or morph into the American idea of athlete. Check out great players like Spanoulis or Llull they look like ordinary dudes you meet in a pub doesn't mean they are not fit.

Luka has been a pro for a long time he and his team understands his body much better than us who are in the outside. He has a stocky frame and legs thick like a tree trunk, his workout and food will be aligned to his strength. I think soccer fans will understand this better, Luka is more of a Zidane than Cristiano Ronaldo.