I know that Ken Rosewall beat Rod Laver in some important matches, even though Laver hit topspin off both sides and Rosewall barely ever used any topspin. I know that Jimmy Connors sometimes beat Bjorn Borg and Aaron Krickstein, even though they used modern technique and Connors hit the ball remarkably flat. But this was still in the days of wooden rackets (or their near equivalents).
All the pros today use modern technique, but the game is so competitive today that they cannot afford to forego even a very small advantage. So how much of a difference does it really make; particularly at lower levels where we're not talking about the very best of the very best?
For example, how much worse off is John McEnroe as a sixty-year old for still using the continental grip? Are there lots of non-name players his age who could beat him because they transitioned their groundstrokes to the new technique, but he didn't?
HUGE.
A continental grip player will get his butt kicked. That's not a grip for base liners or any kind of power player. Pete had an Eastern grip and he had immense power and spin on his forehands. It's not just the grip. Modern forehand uses angular momentum. Open stance forehands were a novelty in those days - mostly used when pulled wide. But, most Spanish players use open stance which allows for more options. Then there is reverse forehand (buggy whip). Players of yesteryears would not use this type of forehand popularised first by Sampras on the run. Nadal took it to a different level.
The racket preparation (on the same side of the body) for ATP forehand allows for more pop. The takeback with racket pointing at the opponent (Sock, Thiem, Kyrgios) allows for racket to snap a longer distance and impart more spin.
On the backhand side, I can only think of Wawrinka taking it to a different level by opening up his body. Traditionally, single handed backhands were executed with a closed stance (Fed). We all know how powerful Wawrinka's backhand is.
I don't think double handed backhand has had a lot of technique changes but I haven't been paying attention.
Volleys clearly have suffered because the modern players do not know how to volley Sampras or Edberg or Becker or McEnroe style. In that department on a fast carpet, McEnroe would eat the modern players alive.
Serve - I don't see a lot of change. But then no one can serve like Sampras. He was the best server of all time and he had a unique serve motion. Same goes for McEnroe.. That body turn on serve is not easy.
Another point about forehand. Modern players like Nadal hit different. It is difficult to describe outside a tennis court. After you hit the ball, you sort of fall backwards (sounds counter intuitive, right?). Think about hitting an off forehand. Now hit every forehand like that but in different directions. The ball will have side spin and top spin. Oscar Wegner described that forehand here:
Players of yesteryears would not have hit like that. So, the technique that has evolved makes a huge difference.
