Originally Posted by tennis_pro
What more data can I use? Federer hits his groundstrokes harder and consistently harder while Sampras would loop the backhand 3-4 times before going for a killer shot, serves just as fast (Sampras rarely hit his serve over 125 mph). I agree he has less sting on the volleys but that's expected as Sampras visited the net a lot more often than Federer did/does. You can't just say "one looks at them and thinks it would be a miracle if Federer was somehow physically stronger", it's just impossible to predict how they would fare in competition.