Definition of Tennis Talent and skill
I believe Borg Number One did something like this but here's a possible definition of Tennis Talent. I've probably stolen some of his ideas so forgive me Borg Number One.
1. Ability to hit with great power off both sides.
Some players like a John Newcombe for example had the ability to hit with great power off his forehand but his backhand, while consistent was not an attacking shot. It leaves a vulnerable point. Some excellent examples today would be Djokovic and Murray. A few years ago Agassi was an ideal example. Laver, Connors and Arthur Ashe were great examples in the past.
2. Having a great overall serving game, first and second serve. The serve is the most important part of the game. Some players like John Doeg in 1930 won the US Championship mainly on serve. Guys like Sampras, Kramer, Ivanisevic, Hoad, Serena Williams and Gonzalez are ideal examples of this.
3. Having great mobility. By that I mean speed, footwork and anticipation. Players like Tilden, Gonzalez, Borg, Rosewall, Djokovic, Connors, Murray, Nadal, Federer and Sedgman are among those who excel in that area. Nadal and Federer have the ability to run around their weaker backhands to pound their forehands. Chris Evert is a great example of anticipation while Goolagong or Kim Clijsters is an example of all of this. Margaret Court was very underrated for her mobility.
4. Great reflexes. That's pretty obvious especially at the net where split second reflexes determine whether you'll hit a winner or get passed but also other areas. Players like Sedgman, Edberg, McEnroe, Laver, Hoad, Borg (yes I know Borg wasn't known for net play but people thought he had perhaps the fastest hands in tennis) are good examples of this. Navratilova is the best example I can think of among the women.
5. Racquet speed. Racquet speed has always be important in determining the outcome of any match. Nowadays I believe it's more important than ever. For example Nadal hits with the most rpms in tennis today which allows him to hit with huge topspin giving him great safety and the ability to make incredible shots. Borg was a great example of a player with incredible racquet speed. Vines' great windup and racquet speed gave him enormous power.
6. Being a lefty. Definitely an edge over right handers because players aren't use to facing them. Players like Laver, Connors, McEnroe, Ivanisevic, Tanner, Navratilova and Nadal are great examples of this.
7. Great stamina. Over the course of perhaps five sets or even three sets great stamina will allow the player to play at near their top level and will wear down other opponents.
8. Agility. Some player just never seem to be in the right position or cannot recover quickly from their previous shot. I think of a player like John Isner, who while he had the talent of great height to hit a super serve, well that same talent hinders his agility in my opinion. A player like Gonzalez or Sampras have excellent height but also were very agile.
9. Touch. It's not just drop shots but lobs, both topspin and slice, different spins, angles, changes of pace, disguise in their shots. Players like Laver, Gonzalez, Tilden, McEnroe, Riggs and Rosewall excelled in this area. Rosewall however didn't have the changes in spin but he was superb in other areas. Borg and Connors are excellent in changes of pace, spins, lobs and disguise.
10. Where to position themselves. Often I'll see a player in which he or she maneuvers the opponent out of position, the ball is floating high at mid court just asking to be volleyed away and the player retreats to the baseline to hit a titanic topspin groundstroke giving the opponent time to recover. Players like Chris Evert, Rosewall, McEnroe, Laver, Gonzalez, Edberg, Segura excelled in this area.
11. Consistent strokes. The ability to hit the ball solidly, keep the ball in play with powerful shots. Perfect examples would be players like Connors, Agassi, Rosewall, Riggs, Kramer and Lendl. These guys rarely mishit the ball and seems to always hit the ball on the sweet spot. Some players may hit a few beautiful shots and look good but they may mishit or not be as accurate as these players. These players have a consistent high level.
12. Mental strength. The ability to stay calm under pressure and hit strong shots. The ability to know what shot to hit in situations. Players like Laver, Borg, Gonzalez, Kramer, Nadal, Tilden were fantastic in this area.