Roger Federer won three majors and 68 matches in 2007; he also proved he was human by losing nine times, the most L's he's had since 2003. On the eve of this year's Australian Open (Jan. 14-27), every player speedy enough to return his line-painting shots wants a crack at the player many consider the best in history. Repeatedly getting balls back can frustrate Federer, and if those shots come at him with depth and pace, his forehand falters and the unforced errors come in bunches. Some say Federer, who finished as 2007's No. 1, is as good as ever. But these six players have shown enough game to prove he's at least touchable.
David Nalbandian -- He may have famously dubbed tennis his profession rather than his obsession (that's race car driving), but when the No. 9 Argentine is focused -- as he was when he won in Madrid and Paris -- he can flummox Federer. "Nalbandian drives the ball into Roger's backhand corner and can also go down the line," says ESPN analyst Pam Shriver. "It's a matchup Federer is uncomfortable with." Clearly: He's one of only three players to beat Roger twice in '07.
Rafael Nadal -- The three-time French roi is ungodly strong and lefthanded; the southpaw stroke means Nadal can pound away with his forehand to Federer's backhand, his weaker side. Nadal makes every point a grind, which taxes Federer and makes him grunt and miss. Nadal has been No. 2 behind Federer since 2005 and owns him on clay. But that five-setter in July's Wimbledon final hints that Nadal is just about ready to meet Federer anytime, on any court.
Fernando Gonzalez -- The No. 7 Chilean pushed Federer in last year's Australian final and still lost for the 10th straight time to the world's No. 1 player. But during his three-set win in Shanghai to break that streak, Gonzalez served well and tricked Federer with his backhand more frequently than normal; a huge forehand is Gonzalez's trademark shot, and it plays big on hardcourt. "Gonzalez is a high-risk player who rides on confidence," Shriver says. "He just believed it was his time." His time may come again.
Novak Djokovic -- This Serb charged all the way to No. 3 in 2007. His versatile game suits all surfaces, and at 20 he's the most likely candidate to take over No. 1. On the hardcourt at the Rogers Cup in Montreal, Djokovic attacked Federer's too-short backhand, then sent forehand winners down the line. Federer finished with 48 unforced errors, Djokovic with the win of his life. Afterward, Federer apologized to the crowd in French for his stupid mistakes.
Guillermo Canas -- Credit the Argentine for using a 15-month substance ban to improve his backhand and serve. On the hardcourt in Indian Wells last March, he ended Federer's seven-month, 41-match winning streak. Two weeks later in Miami, he proved that first upset was no fluke, beating Federer again. But Roger is safe Down Under: The No. 15 Canas has pulled out of the Australian with tendinitis in his left wrist.
Filippo Volandri -- The Italian may have one of the tamest serves on Tour, but he was solid in his Rome win over Federer, with only 23 errors to Roger's 44. Federer missed routine baseline shots and grumbled postmatch: "I don't know what's wrong. Why should I discuss it with you?" But make no mistake: No. 40 Volandri could have won only on clay, Federer's weakest surface, on this lucky day. Which is not to say that it'll never happen again. After all, a broken clock is right twice a day.
Lindsay Berra is a senior writer for ESPN The Magazine.