Blaming international duty for injuries is a bit pretentious. Injuries can happen anywhere and they are always just as bad no matter where or when they happen. International football happens to be a big part of footballing culture and there isn't any sort of magical aura of unbreakability over the players when they play for their countries, of course injuries happen there too.
On a positive note if the injury is as bad as feared this is as good time as any to get injured. Long summer break coming up and Marko should be ready to go when next season starts. Hopefully he can keep his spirits up as these injuries can be mentally really tough.