Rafael Nadal, Wimbledon champion. Three years ago, it was unthinkable to string those four words together. Nadal lost in the second round at the All England Club in 2005 to Gilles Muller, and looked befuddled doing it. He couldn’t return Muller’s serve. He couldn’t control his forehand or adjust to the low bounces of grass. He seemed out of position, and late to the ball, at every turn.

Nadal’s transformation since then has been nothing short of miraculous. Wimbledon begins Monday and Nadal, the finalist in each of the last two years, has elevated himself from long shot to co-favorite to win the title, alongside five-time defending champion Roger Federer. At the Queen’s Club in London last week, Nadal delivered his best performance on grass, beating the two best servers in tennis — 6-foot-10-inch Ivo Karlovic and Andy Roddick — and world no. 3 Novak Djokovic in successive matches. That’s as difficult a draw he’s ever faced in any tournament, and he aced it.

Confidence, dedication, and tactics have played equal roles in Nadal’s ascent on grass. A win at the French Open always lifts Nadal’s spirits, but this year’s title in Paris has given him more confidence than ever. He didn’t lose a set the entire tournament and lost four games in the final against Federer. Compared to years past, he’s better rested, both mentally and physically. His win at Queen’s Club will only increase his belief.

As for technique and tactics, Nadal has steadily improved his game in the last three years. Even on clay, he no longer relies on defensive wizardry as he once did. He hits harder, flatter, and deeper forehands from time to time, more often on grass. Nadal’s topspin forehand gives opponents fits on clay because it bounces so high. On grass, the topspin has another use: Anyone who approaches the net has to lunge to volley a dipping passing shot. Numerous times in the Queen’s Club final, Djokovic popped up a volley and then watched the next shot sail past him.

Nadal’s game works well on grass for two other more subtle reasons. His left-handed serve is the weakest part of his game — but grass, as Andy Roddick explained last week, improves it.

“I think the thing that helps him out the most as far as surface is the grass really helps out his serve,” Roddick said. “He gets kind of the lefty hook in there. It really stays low. If you leave a return hanging, he’s very good at taking that first ball and hitting it.”

On hard courts, Nadal’s serve sits up and begs to be punished. On grass, it keeps his opponents off balance and gives Nadal room to operate.

Nadal’s footwork is perhaps the most important ingredient to his success on grass in recent years. Clay and grass are the sport’s slippery surfaces. On clay, players remain balanced by sliding to a stop. Sliding on grass, however, results in stumbles and tumbles. Unlike Djokovic, Nadal rarely loses his balance. On clay, he slides only when necessary and one rarely sees him do it on hard courts. If there’s a weakness to Djokovic’s game (besides his occasional inability to suppress frustration), it’s his body control. A coach of a top player recently described Djokovic to me as “wobbly,” a word that perfectly suited the Serb’s unbalanced movement in the Queen’s Club final. On hard courts, Djokovic can get away with that. On grass, he finds himself out of position.

The paradox of Nadal’s ever-improving grass-court game is that among the top three seeds, he remains the most vulnerable to outliers (his serve, though more effective on grass, does not produce many free points, so it’s more difficult for him to compensate for lapses in the rest of his game). The earlier part of this tournament might be the trickiest for him, yet once he’s into the quarterfinals, he’ll be very difficult to beat, perhaps more difficult than Federer and certainly Djokovic. This year, there are fewer early-round threats to Nadal. Jo-Wilfried Tsonga, who pummeled Nadal at the Australian Open and plays his best tennis on grass, recently had knee surgery. Radek Stepanek may miss the tournament. Tomas Berdych hasn’t played well since returning from an injury. Other powerful, go-for-broke players — the kind who trouble Nadal on fast surfaces — are slumping (Richard Gasquet, Marcos Baghdatis, Mikhail Youzhny, and Dmitry Tursunov, to name a few).

With those men either missing or hurting, Nadal should have an easier path when the draw is disclosed today (he might get so lucky as being in the opposite half of the draw as Federer and Djokovic, who could be drawn as potential semifinal opponents). Karlovic could pose a problem for Nadal, and so could a player such as Philipp Kohlschreiber, the high-wire act who lost to Federer in last Sunday’s final in Halle, Germany. James Blake has given Nadal trouble before, but he’s nowhere near as effective on grass as he is on hard courts. Robin Soderling extended Nadal to five sets at Wimbledon last year, but his mind is no match for the Spaniard’s. One could add a few hard-hitting, big-serving youngsters — Ernests Gulbis, Jeremy Chardy, Marin Cilic — to this list, but even then, it’s hardly a frightening collection of would-be upset artists.

Federer has won 59 straight matches on grass. If he wins another seven this year, he breaks Bjorn Borg’s record of five consecutive Wimbledon titles. If Nadal wins, he’ll be the first man to win the French Open and Wimbledon back to back since Borg in 1980. Once again, history is on the line at Wimbledon. This time, though, Federer might not be the one who makes it.

Mr. Perrotta is a senior editor at Tennis magazine. He can be reached at tperrotta@tennismagazine.com.