John Isner’s serve is a study in leverage, trajectory physics and efficiency of movement.

He bounces the ball between his gangly legs, taps it with his racket and neatly catches it off the ground in his left hand. He gives it a light, fingertip toss and it hovers there for a split second at the apogee, 11, maybe even 12 feet off the surface of the hardcourt. He shifts his weight to his front leg as his body leans into the stroke, and he gives a little jump just before the moment of impact, stretching his 6-foot-9 frame to its limits.

When the serve works the way it’s supposed to, the ball moves up to 140 miles per hour, strikes at the back corner of the cross-court box and comes off the ground at a steeper angle than it came in.

We know Isner as a local guy — a Grimsley High School grad who grew up in Greensboro. But in the tennis world, he is known for that devastating serve.

When Isner played 5-foot-11 David Goffin in the quarterfinals of the Winston-Salem Open last week, the serve often came in above the Belgian’s head, sending him flailing after it with his racket askew. Goffin took a set off Roger Federer in this year’s French Open, but against Isner he looked like a little kid playing his much bigger brother.

Almost powerless against the serve — Isner scored 12 aces in the first set alone, and four more in the tiebreaker set — Goffin’s best bet was to keep the ball low to the ground, forcing Isner to play well below his center of gravity, to minimize his own unforced errors and, when looking down the barrel of that explosive serve, just try to get his racket head in front of it and hope for the best. Still, with 21 aces overall, Isner won in two straight sets — though you had to give Goffin credit for hanging in there, especially through that long tiebreaker set to end the first.

The server is at an advantage in the game of tennis, putting the ball into play and able to set for its return. But service alternates, and because a set must be won by two games, a player cannot win unless he eventually breaks his opponent’s serve. A big serve can get you far in professional tennis — and Isner may have the biggest serve on the tour — but a player cannot win titles unless the other fundamentals are in place.

Frenchman Jo-Wilfried Tsonga came into the Winston-Salem Open in the first seed, ranked as the No. 6 tennis player in the world, reaching the semi-final against Isner after soundly defeating Spaniard Marcel Granollers with strength and athleticism.

Tsonga, 6-foot-3 and in excellent physical condition, looks like he could play any sport he wanted to at the professional level. He has the upper-body strength to absorb one of Isner’s 140 mph rockets… if he can get to it. But over the course of his three-set victory over Tsonga, Isner fired 24 aces.

How do you beat this guy? His serve is at times un-returnable.

His racket work is superb. He’s quick, and can cover the entire court in just a couple of steps. And forget about tiring him out — remember, John Isner holds the world record, with Frenchman Nicolas Mahut, for the longest tennis match in the history of the sport, just over 11 hours, that ran from Tuesday through Thursday at Wimbledon in 2010. He can literally play for days.

Isner’s opponent in the finals, Czezh Tomas Berdych, had few of the disadvantages the others did. Standing 6-foot-9, he’s theoretically tall enough to handle the monster serve. And he’s got a powerful one himself. Plus he’s a more seasoned player, with plenty of tricks in his trick bag and solid fundamentals.

And it was a close one that could have gone either way — Berdych dominated the first set, winning 6-3. But then Isner found his groove, breaking Berdych’s serve in the first game of the second set and riding nine aces for a 6-4 win.

The last set ended in a prolonged tiebreaker set that saw four lead changes before a drastic forehand by Isner got past Berdych at the end of the two-hour match.

Isner has won both Winston-Salem Open tournaments, and has become closely associated with the event that takes place so near his hometown. This is good news as long as Isner’s star continues to rise — at No. 9, he is the highest seeded American at the US Open, which begins in New York City this week. But crowds for matches other than Isner’s were sparse, especially after Andy Roddick lost to Belgium’s Steve Darcis in a drawn-out contest early in the week.

Isner, whose tennis career is accelerating as fast as one of his hard, angular serves comes off the hardcourt, enjoys playing the tournament for now, staying at his parents’ house in Greensboro and playing with his dog. But for the open to survive for generations of tennis stars to come, we will either have to cultivate more serious fans of the game or hope that another phenom will rise from our midst to bring in the hometown crowds.

But until then, we will have Isner’s soaring figure, his affable countenance and, most importantly, his cannonball serve to lure people out to the Wake Forest Tennis Center as easily as it baffles his cross-court opponents.