Motivation never a factor for Federer

Roger Federer, on the other hand, really, really likes tennis.

Unlike Serena Williams, who recently announced an ambivalence toward the game that has been evident throughout most of her career, even at the age of 30, Federer remains the eternal 12-year-old.

"I'm always excited," he said after his first match in Melbourne, deftly deflecting a question about pressure. "I felt it actually walking down that Walk of Champions, getting out on court and feeling like I have good intensity and am excited to see the Aussie crowd.

"I was anxious to find out how I was going to play, how my opponent was going to play me. So, yeah, I was really excited and a little nervous going into it."

Federer, naturally, dismissed Russian qualifier Alexander Kudryavtsev in straight sets. He is a gym rat, a student of the game, who somehow manages to make every day an opportunity for breathless discovery. Sort of like a certain Patriots quarterback. Tom Brady, too, has taken all the doubts and skepticism about his ability at an advanced age and turned it into, well, W's. You get the idea that both of them -- among the very best of all time in their respective sports -- will manufacture that criticism, even when it hardly exists.

Federer's third-round match, played early Friday afternoon in Melbourne, presented a bigger challenge than Kudryavtsev, way bigger. Ivo Karlovic is 6-foot-10 and serves absolute peas. Last year, the rangy Croatian averaged more than 17 aces per match -- well ahead of John Isner and Jo-Wilfried Tsonga. In the third game of the match, Karlovic laughably won all four points with aces -- against the man many consider the greatest tennis player ever.

Only Federer wasn't laughing. He had to save a set point in the first-set tiebreaker, and then won it by hitting an improbable ball over Karlovic and then banging back a Dr. Ivo offering with a ludicrous backhand cross-court winner.

It was a taut match, but Federer won 7-6 (6), 7-5, 6-3. Federer has taken 10 of 11 matches against Karlovic, but 14 of the 28 sets have gone to tiebreakers.

"I knew going in it was going to be tough," Federer said. "We've played some 'breakers. I knew it would come down to a few [points] here or there. I started to play better as the match went along."

Hunger. Desire. Fire. These are the reasons Federer's game has traveled so well into his 30s. A number of the analysts we've recently talked to think Federer -- owner of a record 16 Grand Slam singles titles -- still has a major or two left in him. Which means it's worth comparing his past few years with the No. 2 all-time player, Pete Sampras, who left the game with 14 majors.

Paul Annacone has the best seat in this house, since he coached Sampras down the stretch and is currently coaching the Swiss champion, along with Severin Luthi.

"For Pete, there was much more wear and tear by this stage," Annacone told Joel Drucker in late December for a Federer profile in Deuce, the ATP World Tour's online magazine. "Roger has the enthusiasm of a 20-year-old. There is no need to motivate him.

"He's relentlessly studious about trying to improve."

Physically, Federer's whisper-quiet, noninvasive game has left him in reasonably good shape. He may have lost a half-step, but he has compensated by being more aggressive and relying on his exclusive memory bank of 998 matches. If he can get past the winner of Bernard Tomic versus Alexandr Dolgopolov, the quarterfinals (against Juan Martin del Potro?) would be No. 1,000.

After his 26th birthday, Sampras won a total of four majors; Wimbledon three years in a row from 1998 to 2000, and finally, the 2002 U.S. Open at the age of 31. It's worth noting that a 29-year-old Sampras went 0-for-4 in 2001.

Federer already has five majors after turning 26. He, too, went 0-for-4 as a 29-year-old. But while Sampras was losing in the first, second and fourth rounds of the other majors -- while reaching the U.S. Open final his last two years -- Federer played at a higher level. After losing to Djokovic in the semifinals of the 2011 Australian Open, Federer beat him in the semis at Roland Garros, ending a 43-match winning streak. At Wimbledon and the U.S. Open, he led Tsonga and Djokovic, but ultimately lost in the quarters and semis, respectively. Federer famously had two match points against Djokovic.

The clock is ticking, even if Federer doesn't openly acknowledge it. Last year was the first year since 2003 that Federer didn't bring home a Grand Slam singles title. It would be a bad precedent to go 0-for-8. Australia seems like as good a place as any to change the karma.

Greg Garber is a senior writer for ESPN.com.