Roger Federer can play shots that only a tennis genius can produce. While Federer's brilliance is undeniable, his losing streak to Rafael Nadal makes me wonder: was his genius magnified by the fact he was playing people like Lleyton Hewitt and Andy Roddick in major finals who could not take advantage of his vulnerabilities the way Rafael Nadal can?

That's one of the challenges of rating players beyond their generation as I did in statistically examining the greatest players of all time:  Federer is unquestionably a great champion, but was his dominance due in part to the fact that there was no one to push him except Nadal?

Pete Sampras, for example, had Andrea Agassi at his best (at least most years), Boris Becker, Jim Courier,  Stefan Edberg, Gustavo Kuerten, Richard Krajicek, Michael Stich, Goran Ivanisevic, Michael Chang, Marcelo Rios, Ivan Lendl, Petr Korda, Thomas Muster etc.

It seems to me that the competition was a lot stronger than the competition Federer has played over the years.  Now I think it's changing with Nadal as No. 1 and Andy Murray and Novak Djokovic both improving. Federer's foes in the top four are all quick and Nadal, Murray and Djokovic all have better backhands.
 
I was recently watching a highlight tape of Rod Laver against Ken Rosewall from the 1972 WCT Championships and Laver hit a number of shots, backhands and forehands, literally inches off the court as he took the ball on the rise. Granted, the pace and spin of the shots — because wood-racquet era players had a much smaller string surface to work with — is not nearly what it is today, however I don't see Federer or the other top three players taking the ball as early as Laver did. Arthur Ashe pointed out one of the problems playing Laver was that he hit the ball so early on the baseline that he stole reaction time from you and though Federer takes it earlier than Nadal he does not consistently do it as Laver did.
 
Federer essentially is a great defensive baseline player with one of the most powerful and lethal forehands in tennis history.  His movement is as good as anyone's and he's smoother than a player like Nadal, which helps him last through the tough tennis yearly tournament grind. Though he is often described as an all-court player, watch closely: Federer today, like most players on the ATP Tour, counterpunches from the baseline. The difference is Federer can punish players with a pulverizing forehand that no one else hits as well.

When people view Federer's five straight losses to Nadal a common remedy they propose is for Federer to serve and volley more often.

I know Federer beat Sampras in the 2001 Wimbledon fourth round by routinely serving and volleying, but he rarely serve and volleys now and when he does you can't put Federer in Sampras or John McEnroe's league as a volleyer.

By virtue of winning Roland Garros, Wimbledon, the Olympic gold medal and the Australian Open in the past eight points Nadal has 14,260 ranking points and is appearing invincible. If you watch his demanding physical style of play, however, you have to be concerned about his long-term health, particularly given the fact he's had knee problems in the past.

Nadal is often compared to Bjorn Borg and it's easy to understand why: he is the first man since Borg to win the French Open and Wimbledon back to back. But go back to the video tape: Borg was a much smoother mover than Nadal.  Borg was very light on his feet — remember his French Open match with Vilas where Vilas' socks were caked with red clay after the match while Borg's socks were barely stained — the fact that Borg was so light on his feet helped him in long matches and throughout a long season.

Nadal is built more like Vilas than Borg: he has a very muscular, powerful upper body, which enables him to generate a lot of racquet-head speed on the run and hitting an open-stance forehand, however you have to wonder if the accumulation of wear and tear on his body will take a toll.

There is a lot to like about Nadal's game: he continues to work hard and improve all aspects of his game. I would argue he volleys even better than Federer now and his serve, especially on the ad side, is much improved.  He has changed his groundstrokes so his backhand is a major weapon now and for the Australian he flattered out his forehand a bit so he had more penetration on that side.
 
But with the exception of Nadal's blow-out win over Federer in the 2008 French Open final, his margins of victory are not always great and the energy he exudes in majors can be draining. When John McEnroe was at his peak in 1984 he was so dominant it sometimes seemed no one could handle him. The same can be said of Sampras at his best on grass or Laver in his prime. 

I don't get that feeling with Nadal, whose game is based more on attrition than the pure shot-making explosiveness of a Laver, McEnroe or Sampras. I remember Jo-Wilfried Tsonga demolishing Nadal in the 2008 Australian Open semifinals and Nadal seemed helpless against the attacking Tsonga game. Nadal still tends to play from so far behind the baseline he nearly dares you to use the short court as Tsonga did, but very few top 20 players volley with the finesse and flair of Tsonga. As great as Nadal is now — and I do believe he will get better — I don't feel he can go into overdrive and dominant another champion (except on clay) as McEnroe, Becker, Borg or Sampras did.

Raymond Lee is a tennis historian and Tennis Week contributing writer from New York. His recent features include "Flash Points: Matches That Changed The Course Of Tennis History".