It's tough to decide what's most impressive about Novak Djokovic's 37-0 record in 2011, the best start in men's tennis in more than a quarter-century.
Djokovic has won all seven tournaments he's entered, including the Australian Open; he never had collected more than five titles in a full season. He's a combined 7-0 against Rafael Nadal and Roger Federer, two men who dominated him and the sport the past several years. He's 13-0 against all top-10 players. He leads the ATP in return games won and is second in service games won.
The No. 1-ranked Nadal summed it up simply, saying: "He is doing amazing things."
Nadal should know.
He is 0-4 against the second-ranked Djokovic this season, including straight-set losses in the finals on clay at Madrid and Rome this month. Those matches - and Djokovic's body of work all year - completely change the dynamic heading to the French Open, the clay-court Grand Slam tournament that begins next weekend.
"Nadal doesn't seem to know what to do against him, and quite honestly, if Nadal is baffled by playing him, then that just shows you how great he's playing on clay," seven-time major champion John McEnroe said in a telephone interview Monday. "You're looking at a guy who's the best player in the world right now."
McEnroe owns the Open era mark for best start to a season, 42-0 in 1984, which Djokovic would surpass by reaching the final in Paris. McEnroe will be there as an NBC analyst, including for the June 5 men's championship match.
"It's probably the one record - or one of the few, if any - I have left. That would be the bad part. But at the same time, the good part is it's given quite a real shot in the arm to tennis, which I'm quite happy about," McEnroe said. "There's some excitement going into the French. There's something really to talk about."
Nadal has won five of the past six titles at Roland Garros; Djokovic never has made it past the semifinals there. But Djokovic, who turns 24 the day the French Open starts, has the momentum and mental edge at the moment, including this tidbit: He is the first player to beat Nadal twice on clay in one season.
"Let us be clear: He is the 'King of Clay,' and he is the best player ever to play on this surface," Djokovic said after beating Nadal 6-4, 6-4 in Sunday's Italian Open final. "I have won against him twice in the last eight days, which I think is incredible, an incredible achievement for me, and has given me a lot of confidence for the French Open."
Listen to Djokovic enough, and you'll hear that word "confidence" over and over again.
He credits his recent run to a boost of self-belief he got while helping Serbia beat France in December to win its first Davis Cup. Djokovic won two matches during that final, the start of what now has become a 39-match winning streak overall - seven away from Guillermo Vilas' Open era record of 46 in 1977.
"I've seen a lot of maturation in Novak," 14-time Grand Slam champion Pete Sampras said in a recent telephone interview.
"I've seen him play a number of times over the years, and he was at the level with Roger and Rafa, but you never felt like his temperament could withstand a four-hour match. It always felt like he was a little bit up and down, a little bit emotional," Sampras added. "And this year, something clicked in him, where he just sort of became a little bit more positive."
Djokovic acknowledges he'd been waiting, as he put it Sunday, "for everything to come together." He entered this year 13-29 total against Nadal and Federer, who finished ahead of him in the rankings the past four seasons.
His movement - "He's like Gumby out there," McEnroe said - groundstrokes and return of serve quickly made Djokovic someone to watch when he turned pro at 16, and he really began to draw more widespread attention a few years later. In 2007, he made the semifinals at the French Open and Wimbledon, then was the runner-up to Federer at the U.S. Open.
Djokovic made a splash in New York after his quarterfinal that year when, prompted by a TV interviewer, he did perfect impersonations of Maria Sharapova (pretending to tuck his hair behind his ears, exactly the way the Russian does) and Nadal (even yanking at the back of his shorts, exactly the way the Spaniard does).
There were those who wondered when Djokovic's play would catch up to his personality. There have been questions about his fitness and mental strength, in part because he cited injuries when quitting during several matches at important tournaments.
Clearly he is a different player now. He won his first major title at the 2008 Australian Open, was the runner-up to Nadal at last year's U.S. Open, then added his second Grand Slam trophy in Australia in January.
Against fourth-ranked Andy Murray in the Rome semifinals last week, Djokovic was two points from defeat three times. But he came back to win in a third-set tiebreaker.
"It took him a few years to find his way," Sampras observed, "and now he has that aura now where he's really, really tough to beat."
Djokovic also has a great chance to earn his first No. 1 ranking. According to the ATP World Tour, Nadal will stay at the top only if he wins the French Open and Djokovic loses before the final. Or put another way: If Nadal doesn't win the tournament, Djokovic will rise to No. 1 - no matter how he fares in Paris.
As it is, the tour announced Monday that Djokovic is the first player to qualify for its season-ending championship in London.
"Today I am definitely not thinking (about) losing a match," Djokovic said Sunday in Rome, "and thinking only of winning."
So far this year, he's done nothing but win.