NEW YORK -- Dubai is the largest city in the United Arab Emirates, a shimmering oasis of glass and steel skyscrapers. It sits on the west side of the Arabian Peninsula, along the Persian Gulf.
The vast reserves of oil beneath give Dubai one of the highest per-capita incomes on earth. Beyond opulence, the other constant among the world-class hotels and restaurants is the unforgiving sun. On most days, it is blazing hot.
In February, in the wake of his crushing loss in the Australian Open final to Rafael Nadal, Roger Federer retreated to his favorite training base. With the temperature usually in triple digits, he practiced four and five hours a day, working his way through a slew of hitting partners.
Darren Cahill, Andre Agassi's former coach and an ESPN analyst, saw that sweat equity with his own eyes. He worked with Federer for nine days as they discussed a possible coaching role.
"Roger's a sneaky-hard worker," Cahill said earlier this week. "He gets to the tournament and in practice all he's doing is trying to groove his shots, slap the ball around and hit some different spins. Little do they know, this guy's been grinding away on the back courts somewhere else."
In the narrow span of eight months, Federer lost three Grand Slam finals to Rafael Nadal: the 2008 French Open, 2008 Wimbledon (hailed widely as perhaps the greatest match ever) and the 2009 Australian Open. A bout with mononucleosis and an aching back appreciably reduced his effectiveness in 2008.
Only a win at the U.S. Open, his 13th major, salvaged his worst season in more than five years. The question was no longer how badly Federer, then 27, would eclipse Pete Sampras' record of 14 major titles. It was whether he would break it at all.
Federer cried shamelessly after his loss in Australia and smashed his racket in frustration during a loss to Novak Djokovic in Miami. Bjorn Borg, who had seen those tears, was interviewed in March by ESPN. It was as if he could see the future when few others could. Perhaps it was a champion recognizing a rare peer.
"He has a mental thing now playing Nadal," Borg said. "Rafa has an advantage with that. So mentally for Roger it's tough. But Roger is a great champion. For me, he's the best player to ever play the game. He's going to come back. He wants to come back."
Pete Sampras, with little evidence to support his premise, also predicted the return of the man who would soon break his Grand Slam record.
"Nadal's right there, and he's his nemesis," Sampras told ESPN before the French Open. "It's going to push him to try and beat him. Maybe it's what he needs a little bit. Maybe he needs to add something to his game against Nadal to beat him.
"Maybe come in a little more, mix it up. But it'll be good for him. He's got another four, five years, Roger, and I think he'll look at this time as frustrating, but I think it will be good for him."
Sampras spoke with a certainty that could only come from experience.
"It was good for me when Andre [Agassi] started beating me," Sampras said. "It made me a better player. I added things to my game that, against most guys, I didn't have to do. Against Andre, I had to serve and volley on my second serve.
"He just forced me to be a better player. And I think Nadal will do that for Roger."
And that's precisely what happened.
Federer won the French Open and Wimbledon earlier this year, and now he has a chance make it three-for-four with the U.S. Open title. He beat Novak Djokovic in Sunday's semifinal and now, seeking his sixth consecutive championship, plays Juan Martin del Potro in Monday's final.
"Roger made everyone better," Cahill said. "Then it was Rafa's turn."
Addressing his deficiencies
The intriguing question surfaced after Federer won his first-round match. How much of his recent success was due to the challenge of Rafael Nadal? Has his place in history been advanced by the appearance -- by the surprising dominance -- of the swaggering Mallorcan?
"Potentially," Federer said, weighing his words. "I think this is stuff you can talk about when my career is over, really. This is when you analyze, 'OK, how much did Rafa Nadal help my career and how much did I help his career?'
"I can't answer this."
Federer had already won four Grand Slam singles titles when he met Nadal in the semifinals of the 2005 French Open. The 19-year-old handled the world No. 1 with relative ease and went on to win the first of four consecutive titles at Roland Garros. After reaching the finals on grass at Wimbledon in 2006 and 2007, Nadal went one step further in 2008.
Thus, after holding the No. 1 ranking for a record 237 consecutive weeks, Federer relinquished it to Nadal in August 2008.
Nadal, like Federer, was never completely satisfied with his game. He improved his backhand. He empowered his serve. He tinkered with his return position. He stayed hungry -- insatiable, really. Cahill said Nadal is as mentally strong as anyone he's seen.
"Whenever someone comes in and distances himself from the pack, some people get together and work out how to close the gap," Cahill explained. "That, to an extent, is what Rafa did. He wasn't the only one doing it, but he was the first and the fastest. And he took the game to a new level, not so much from a technical standpoint, but more from a physical point of view.
"Roger realized that he needed to address the physicality. He had to evolve his game to answer the questions that Rafa's game kept posing."
The Nadal camp, according to Benito Perez-Barbadillo, has not discussed the specific effects of Nadal's success on Federer's game.
"No," Perez-Barbadillo, Nadal's close friend, said on Friday. "Not at all.
"The one who benefits from this is tennis, not Federer. If Rafa hadn't come along, Roger would have won many more Grand Slams. And, without Roger, Rafa would probably have won more Slams.
"Roger has won [nine] more, but you see this great rivalry and it's good for history and good for the sport."
Jose Higueras was retained by Federer last year during the clay-court season. Now the USTA's director of coaching for developing elite players, he had an insider's view of Federer's most frustrating season.
"I think it became clear to Roger when he was not feeling well that to beat Rafa he had to be in top shape," Higueras said. "His movement had to be more precise to beat Rafa."
So Federer went to work in Dubai at the end of the 2008 season, and again in February, with renewed purpose. Beating Rafa was his greatest motivation. He worked harder than ever with trainer Pierre Paganini.
The physical change is striking. Federer is playing, those close to him say, about eight pounds lighter than his listed weight of 187 pounds.
"Slowly," Higueras said, "his body has come back. He's where he wants to be."
Said Cahill, "The unsung hero of Roger's camp is Pierre. I got a small glimpse into that window and I think the relationship they have is as strong as the relationship I witnessed between Gil Reyes and Andre Agassi. Roger has full trust in what Pierre sets in stone for him."
There have been some other, less obvious alterations. According to Higueras and Cahill, Federer:
• Made his forehand more effective and improved his backhand.
"He's never going to beat Rafa off the backhand side," Cahill said. "Once he got into the mindset that if he could at least stay neutral with his backhand and beat Rafa with his forehand, then he was going to be in a much better position. Now he uses his backhand to set up the forehand."
"In the patterns of a point," Higueras said, "this is what hurt the most: Rafa's forehand to Roger's backhand. He needed to correct this."
• Took something off his serve in the bigger moments.
"I think he also used to press on his serve against Rafa," Cahill said. "He was looking for that extra 4 or 5 miles an hour. And he's always serving his best when he's between 120-126 miles per hour. He relaxes a little more on the serve. He hits his spots a lot better. He's not looking to hit it so hard. He's more about direction than powering through the opponent."
• Embraced the drop shot from the baseline and drop volleys from closer to the net.
"You can't imagine what a difference that one shot makes," Cahill said. "He's mastered it."
It was Higueras who taught Federer that nasty little weapon.
"We introduced that last year," Higueras said. "You have never seen him use the drop shot on the forehand side. On clay especially, that's a great play."
• Came forward more often, sometimes at surprising junctures, even when he didn't want to.
"When he is aggressive," Higueras said, "he is very hard to beat."
Federer's unpredictable dashes to the net -- facilitated by his improved fitness -- helped him defeat Novak Djokovic and Andy Murray in Cincinnati.
Burning to be better
Federer, as we now know, came roaring, soaring back to his place atop the tennis continuum.
He won the French Open, completing a career Grand Slam. He won at Wimbledon, his sixth title at the All England. Certainly, he was enabled by the tender, tendinitis-plagued knees of Nadal, who crashed out of Roland Garros in the fourth round and didn't even play in London.
"Champions know that if you stop getting better, you're getting worse," Higueras said. "This is true at all levels. I mentioned it pretty often to him last year: You have to think in terms of trying to get better, or your longevity suffers.
"Think about this: One guy had a better year than him in 2008 -- one. And now look at what he's done. He could win three Slams in a row."
More than anything, Higueras and Cahill stress, Federer has found his resolve again. After enduring what appeared to be a bruising defeat, a champion has the ability to rewind back to zero and refocus.
"I've seen him after losing matches, and I haven't been around too many people who react like that," Higueras said. "Pete [Sampras] was like that. Roger, I saw last year when he got beat at the French Open. The next day he went to Halle [Germany] and it was like nothing happened."
After looking up at Nadal for 46 straight weeks, Federer regained the No. 1 ranking following his Wimbledon win. Today, Nadal is No. 3 in the rankings and wrestling with a strategy that will close the gap a second time.
"You have to assume [Rafa's] one of the reasons [for his improvement]," said Tony Godsick, Federer's International Management Group agent. "Roger needs competition. He needs challenges to make it exciting for him. He tells you he wants to play the best player in the biggest stadiums – and he means it, he really does."
"I think it was a great, great rivalry we've had so far," Federer said. "I definitely think it increased popularity in the game."
"You have the lefty against the righty," Cahill said. "The guy that's so gritty and tough, and Roger's cool and collected. It's going to be an exciting next five years for the sport."
But in the final analysis, we have Nadal to thank for Federer's marvelous return, although Federer isn't quite willing to admit it.
Greg Garber is a senior writer for ESPN.com.