Ivo Karlovic might be a one-trick pony, but oh, what a magnificent trick lies at this powerful pony’s disposal.

Karlovic, the most fearsome server in all of tennis, rode 46 aces to the finish line on Friday, as the Croatian narrowly defeated France’s Jo-Wilfried Tsonga in four razor-close sets. The 7-6 (5), 6-7 (5), 7-5, 7-6 (5) victory on Court 1 propels the ATP Tour’s bomb-throwing giant into the second week of play at the All-England Club. The landmark triumph also moves “Doctor Ivo” into the fourth round at a Grand Slam singles event for just the second time in 25 career appearances.

When one sees the Karlovic serve, it is initially hard to fathom how this gentle 30-year-old beanstalk of a man hasn’t won more on the pro circuit. At 6 feet, 10 inches tall (2.08 meters for those who follow the metric system)–Karlovic enjoys a body angle relative to the net that makes his serves virtually unreturnable when they’re hitting their spots. While most tennis pros have to power the ball through the service box, the king-sized Croat can get on top of his serves and hit the ball with a more downward trajectory; it sometimes seems that Karlovic’s serve is little more than an overhead smash initiated from the baseline.

Yet, for all of his serving exploits, Karlovic has rarely been able to threaten the world’s top players. He might reach a great many tiebreaks in the matches he plays, but therein lies the peril of being a one-note wonder who lacks the all-around game of other, more proven performers. Goran Ivanisevic–like Karlovic, a thunderous server with a mediocre assortment of groundstrokes–proved to be more proficient as a volleyer, and developed a small but meaningful amount of appreciable consistency from the backcourt. The 2001 Wimbledon champion never lit people up from the baseline, but Ivanisevic did shore up his weaknesses to the point that his all-around game possessed some degree of texture. If he lost one tiebreak set, Goran could mount a comeback.

For Karlovic, that hasn’t been the case.

The world No. 36 hasn’t enjoyed much success at slams, and hadn’t escaped the first round at Wimbledon since his last fourth-round appearance in 2004. It’s assumed that mammoth servers should have their way on grass, but with Karlovic, that line of thought hasn’t been borne out. Bereft of the serviceable groundstrokes owned by Ivanisevic, and not as nimble at the net, Karlovic truly relies on the serve and the serve alone. This means that on any occasion when he’s not serving, the 30-year-old is exposed. He might cruise on all six service games in a given set, but the chances are very high that he’ll barely dent an opponent’s serve as well. This leads to tiebreaks, the element of tennis with which Karlovic enjoys an intimate relationship.

Tiebreakers simultaneously represent Karlovic’s great hope and his worst fear: They can allow Doctor Ivo to win sets and matches without breaking an opponent’s serve, but if Karlovic can’t pull them out, he’s finished. Precisely because he has no other weapons to turn to when his serve doesn’t do the job on a given point, Karlovic has usually found himself outflanked and underequipped when pressure-packed points arrive. No one serves at even 80 percent on a consistent basis, let alone 100 percent, but with Ivo Karlovic’s style of play, missing a first serve–especially in a tiebreak–simply can’t happen. The small margin of error facing the veteran offers insight into why Karlovic hasn’t won more matches.

This is not an underachieving player, mind you; it needs to be said that Doctor Ivo–who has never reached the quarterfinals of a slam, and has therefore never created an expectations monster for himself–is merely a man who is hamstrung by his height when the topic of discussion is not his serve. Karlovic’s 6-10 body simply makes it incredibly difficult for this tall tower to bend down to retrieve slices or any other shots that stay low to the ground. Any player who can hit a dipping passing shot will either draw an error on a Karlovic volley, or force this serving sensation to hit the ball without much of an angle or pace. It’s fair to say that while Ivo Karlovic can render opponents powerless with his mighty serve, opponents can break down the Doctor in several different ways. That reality best expresses why Karlovic hasn’t claimed more scalps on tour, at the slams or in other tournaments as well.

With respect to this match against the ninth-seeded Tsonga–another huge-serving, big-hitting fireballer–the question surrounding Karlovic would be the same query that’s engulfed the 30-year-old for years at the slams: Could he serve well enough long enough to overcome his deficiencies?

Here’s an amazing statistic about Karlovic at Grand Slam singles events, which helps explain why this man has lost the five-setters he’s played: Doctor Ivo entered Friday’s fistfight against Tsonga with an 0-11 record in five-set matches at slams. With the sole exception of the U.S. Open, tennis’s major tournaments do not play a tiebreak in the fifth and final set. This means that when matches go the distance in Australia, France, or here at Wimbledon, Karlovic lacks the safety of the shootout-style format provided by a tiebreak. The Croatian simply has to win tiebreaks, and also win matches in four sets or fewer.

On this day at SW19, Doctor Ivo found the medicine he’d been looking for.

The two men played three tiebreaks, all of them decided by the minimum number of two points, but it was Karlovic who was slightly better in the clutch. Serving with just as much authority in set four as he did in set one, a man who is prone to losing stamina–due to lugging his longer-than-long arms and legs around a court–showed surprising resilience against Tsonga, the 2008 Australian Open runner-up. Karlovic didn’t lose his cool or his focus in the three tiebreaks that were contested, especially in a pivotal fourth-set standoff that–had it gone Tsonga’s way–would have produced a fifth set, Doctor Ivo’s personal Waterloo.

Karlovic biffed an easy forehand volley early in the fourth-set breaker, forfeiting a mini-break lead he had gained just moments earlier. In the past, such a mistake would have made Karlovic crumble, but against Tsonga, the doctor didn’t panic. Down 4-3, Karlovic coolly held his two service points and then–at 5-4–crushed a forehand return on a second serve from Tsonga. By picking his battles wisely, and going for broke only when he could afford to, Karlovic earned two match points at 6-4. The first one came on Tsonga’s serve, whereupon the Frenchman fended off the grim reaper. At 6-5, however, Karlovic had the match on his racket: One serve, one bomb, one ace, and Doctor Ivo would be through to the fourth round. A man who lives by the serve–and who couldn’t last long on the ATP Tour without it–encountered the kind of scenario he must dream of in his sleep.

The Croatian–knowing the importance of this one serve–took a little extra time before toeing the service line. He regrouped, he bounced the ball, he reared back and fired… and smoked an unhittable laser down the middle T of the ad court service box. The deed had been done, and without having to deal with a nightmarish deciding set, Ivo Karlovic–winner of two tiebreaks and bearer of 46 aces, just weeks after hitting a record 55 in the French Open against Lleyton Hewitt–had once again reached the fourth round at Wimbledon.

Giants have their weaknesses–Ivo Karlovic is no exception. But on one fabulous Friday at SW19, a calm Croatian truly stood tall in the saddle.