I was at the Australian Open this year and saw Janko play Ryan Harrison, an up and coming American teenager on an outer court. Janko won in three sets with the last one being a tie breaker. Watching the differences between an experienced veteran and rookie was very interesting. Janko picked his spots...varying the speed of his serves from time to time; hitting attacking, rallying or defending groundstrokes at the appropriate time...not going for winners when he would be better off just getting the ball back deep to give himself time to recover in the court. The biggest difference I saw was that Janko was always looking for an opportunity to attack...Federer does this so well..right after he hits a ball he tries to determine what type of shot his opponent will have to hit back. If his opponent is running to the open court to return a shot, he tries to determine if he will be able to step into the ball and hit a solid groundstroke back OR if he will have to stretch to hit the ball and then perhaps not be able to hit a deep and solid shot back. Janko anticipated this well and came to the net to attack often and put Harrison on the defensive and chasing ball after ball. Harrison tried this tactic only a few times all match and it is something he will have to learn to do if he hopes to move up as a pro.