There has never been a player like Karlovic in the history of tennis. He's the tallest pro to climb high (#37) in the world rankings, and he has, arguably, the biggest serve ever.
In his opening match this week, which he won 7-6, 7-6, he served 32 aces. That's an ordinary day's work for him. In a Davis Cup match last year, he had 78 aces. That broke his previous ace records of 51 and 55. The oddity of oddities is that he lost all three of those matches. He is like a long driver in golf or a home-run hitter in baseball.
Andy Roddick, who beat James Blake Wednesday night in a third-set tiebreaker, serves as hard as Karlovic but is eight inches shorter at 6' 2". Roddick is ranked higher than Karlovic and has won more tournaments because he has a better all-around game.
By pro standards, Karlovic has an ordinary backhand. He usually slices it, and often hits out or into the net when he tried to hit through it with topspin. His Memphis opponent, Benjamin Becker, was able to win the majority of points when he got into rallies.
Roddick has a better all-around game than almost anyone in the world except Roger Federer. Roddick has a faster serve than Blake. But he beat Blake because has a backhand that is as good or better. Blake missed three of them in the tiebreaker. Roddick didn't. Game, set, match.
In the current issue of Tennis magazine, an article by Douglas Robson argues that the serve "isn't what it was once cranked up to be." Some big servers are actually taking something off their serve for the sake of spin, placement, or consistency.
There are three other big big servers in the men's draw — John Isner (6' 9"), Sam Querrey (6' 6"), and Tomas Berdych (6' 5"). Like Karlovic, they're still in the tournament at the midway point. They may foreshadow the first tennis seven-foot pro, a child prodigy with the skills of Roddick and the genes of, say, Pau Gasol.
On the women's side, Maria Sharapova has a 115 mile an hour first serve, faster than most of her overmatched competition in Memphis. But she's not up there with the Williams sisters. Sharapova has won major championships not because of her serve but because of her hard and consistent ground strokes. In fact, she sometimes wins in spite of her serve. Remarkably, she lost last year in the U.S. Open to Melanie Oudin, who is second-seeded in Memphis. Just as remarkably, she almost won despite hitting 21 double faults.