At the pro level, there is vast variation in the height off the ground at which players make contact with their serve, and there are tradeoffs. Hitting the ball at a greater height helps the server get wide angles, taking the returner off the court. Or, for the really tall players such as John Isner, making contact at nearly 11 feet helps bounce the ball so high it is difficult to return. On the other hand, the higher the toss and the greater the leap the harder it is to time the stroke. Let's look at some examples. The larger text indicates the elevation at which their racket makes contact with the ball, while the smaller text gives the player's height. One note, a variation of a few inches between two players isn't meaningful; it's within the variations each player has.
Rafael Nadal is known for his lefty-hook serve. In the close up of the impact, you see how the tennis ball is compressed nearly in half, sticking less than an inch out the back of the racket, stretching Rafa's black, Baboblat RPM strings as fuzz from the blow trails behind.
Roger Federer is known for "serving as if he's 6 foot 5 tall". We checked that premise and it is literally true; Fed leaps so far up he hits the ball further off the ground than players such as 6 ft 5 in Tomas Berdych and Milos Raonic. This is one key to his wide, slice serve in the deuce court and short-wide kicker to the ad side. { continues after 3 images of Fed }
Maria Sharapova recently said with a wry smile that she's used a different serve technique at each of her five 'Slam title wins because of multiple shoulder injuries and surgery. One constant is making the most of her length, extending to hit slice and flat serves. At times, she's hit the ball at greater elevation than 6 ft 5 in ATP player, Tomas Berdych, at others slightly below his mark.
Kei Nishikori is an optimistic 5 ft 11 in or so, and stretches to get every inch he can, striking the ball at 9 ft 1.5 in per video analysis.
Juan Martin del Potro is among the largest of the top, ATP pros, probably reaching 6 ft 7 in {his ancient ATP profile likely cheats him of an inch}, and he's more mesomorph than most pro players. Delpo's serves often reach 135 mph but he's more concerned with hitting a heavy ball than going for max velocity. Here, at the old San Jose tournament, he makes contact at around 10 feet, well into the court.
Ernests Gulbis has one of the best, first serves in tennis with great velocity, spin, and direction. At 6 ft 3 in, Crazy Ernie leaps high, cartwheeling suddenly, snaps violently into the court. The inserts show how much internal, shoulder rotation Gulbis gets
Many think Canadian Milos Raonic has the best, first serve in the history of tennis. At up to 150 mph, wicked movement, and ability to hit every spot, Milos is a perennial ace leader. Milos patterns his serve after that of Pete Sampras, using a deep knee bend to leap up into the ball. Milos is 6 ft 5 in, but has the legs of a 7-footer.
Novak Djokovic, like Fed, is a spot server. That is, his serve is effective because of its location and variety rather than sheer velocity. And, he's awfully good at backing it up.
Andy Murray, another former world number one, is more focused on the velocity of his first serve, reaching the mid-130s, and hitting a lot of slice. Andy also struggles serving into the sun as his squint here at Indian Wells shows.
Ivo Karlovic's game is all about his massive serve. He leads in career aces and has the fastest serve recorded at a top level event, a 156 mph bomb in the Davis Cup {although Aussie fans might note that Sam Groth claims a 163.4 mph shot in a Challenger event.} Ivo's approach to serving is quite different than that of everyone else you've seen here so far. His goal is to get to the net as fast as possible and use his 7-foot-plus wingspan to form a wall. You see here that he barely gets off the ground, pushing into the court, not up, but still hitting the ball at nearly 11 feet.
If John Isner doesn't have the best first serve in history (and many think he does) he certainly has the best combination of first- and second-serve. John hits a heavy, kick serve, striking the ball not only at nearly 11 feet high but a full 4 feet into the court.
While normal tennis players are taught early on that they can't hit down on serves, John quite literally does, spiking the ball as if he was hitting an overhead smash inside the court. That adds to the bounce caused by his heavy topspin, often sending the ball to nearly 7 feet high on the bounce. It's hard enough to return a 135 mph serve that has heavy spin. Try that when the ball is well over your head. Note: An ESPN article claims that Isner's contact height has been measured at 11 feet 11/16th inches, but I don't believe it. The same piece claims his feet were only 2-3 inches in off the ground, and clearly he leaps several feet up. Perhaps they measured the tip of his racket rather but even then that is inconsistent with numerous other reports.
These two screen caps from The Tennis Channel show how Big John's serve leaps off the court. In the first image, serving against Djokovic, Isner's serve topped 7 feet and was still climbing as it passed the returner. In the second, we see a 120 mph serve in the T-corner bounced 5.5 feet high as it reached the returner after 0.745 sec. Source; First TC screen is from Tennis Warehouse discussion thread.
Serena Williams probably has the best serve in the history of women's tennis, with maximum velocity in the high 120s, and good variety. At only a reported 5 ft 9 in tall, she doesn't have much hops either, but oh, those shoulders.
Johanna Konta has an effective, first serve, and can hit slice or kick to all four corners. The right image at slow shutter speed shows how the racket head decelerates at the moment of impact and the ball shoots out.
The 2017 US Open finalist, Kevin Anderson has one of the most-effective serves in tennis. At 6 ft 8 in, he's been criticized by some analysts for not getting as much elevation in hitting his serve as the few, other players of that height. But, you can see that he gets into the court, which means both that he can get to the net in doubles, and the returner effectively has a split second less to react, since the ball is hit feet into the court. In baseball, pitchers that stride a couple of feet closer to the plate, such as Aroldis Chapman get the equivalent of another 5-7 mph on their fastball.
