Well Dimitrov is the highest ranked teen around, and he didn't make his first challenger title until August of this year, so I'll give Krajinovic the same amount of time. Ricardas Berankis who's the best 1990 player, didn't win a Challenger until he was 20, and Thiemo de Bakker didn't do it until he was 21, so he still has some time.
Yeah,that ''young'' players are better and better every year
Lets wait and see what will 2011 bring,I really don't expect anything from Filip and really nothing serious from any of them in ATP Tour (don't think any of them played 15 ATP matches)
Grigor needed just that Geneva title (I watched it and he celebrate like it was Masters 1000 crown) to start great Challengers run but he have talent for much more then that