Originally Posted by mattennis
One of the most important aspects of Federer (that many times passes unnoticed) is that he was as well one of the best defenders (when needed).
Federer serve, forehand, backhand...winners in all kind of positions were absolutely great, but we all have seen great players making a ton of amazing winners in the past.
The thing with Federer is that, when he wasn't winning being the aggresor, he could grind out matches like the best ones (in his prime at least).
I've seen many times where Federer did run endlessly because he needed to do it.
I remember Federer running like crazy from corner to corner in the US OPEN'05 Final (against Agassi) in the second and third sets, because he wasn't feeling confident with his backhand.
I can not imagine Sampras or Agassi doing something like that. Agassi and Sampras would live and die playing their style: aggresion, dictating the points to death.
Obviously they could and would run like crazy in some very important points, but not for an entire match.
Federer has showed countless times in his career that, if needed, he could run and defend like the best ones, and could do it for hours.
That is one of the things of Federer that differentiates him from other great aggresive players from the 90s like Sampras or Agassi or Becker.
Usually, the players that almost always can impose their aggresive game (Sampras, Agassi, Becker,...) and so normally run way less than their rivals, they don't like to be the defending runners at all. They can do it on occasions, some important points, but you didn't see Sampras, Agassi or Becker doing it for hours, they preferred to take even more risks in their shots (and so to make the other guy run more than you again even if upping unforced errors) than to grind out matches.
Federer could and in fact was very good at that as well (very quick, great footwork and special ability to retrieve very difficult shots).
That very important aspect of his game is one of the main reasons why he had so very few losses during his prime. Even when not feeling specially inspired with his game, he could still win because he could and would run and grind if needed to win.
Agassi, Sampras, Becker, they lost many matches in which they looked as if tanking, because if they were doing a lot of unforced errors, instead of trying to cut down errors and be more conservative from the baseline (even if that meant they had to run more because the rival could then dictate more) they went on taking more and more risks in their shots and making more and more unforced errors that looked like tanking.
In that sense Federer could play like a Lendl, Wilander when needed (cutting down unforced errors), and obviously he could be a Becker, Sampras or Agassi taking risks and dictating points everytime he felt confident (the majority of his matches).