Roger Federer continues to move swiftly through the draw

— -- NEW YORK -- Roger Federer has always been the epitome of clean.

His persona, his technique -- his entire being is exceedingly precise. We will refrain (regretfully), from the ubiquitous Swiss watch simile.

At the age of 34, this efficiency is becoming more and more important. Witness the dramatic departure of Rafael Nadal early Saturday morning at the deft hands of Fabio Fognini. Nadal has always hit a heavy, heavy ball and now he's feeling the weight of that enormous effort.

Federer, meanwhile, continues to hover effortlessly above the madding crowd. In a world of talented tennis players, only Novak Djokovic is better at the moment. Federer is ranked No. 2 in the world and, outside of not winning a Grand Slam in more than three years, is in something approaching vintage form.

He knocked off No. 29 seed Philipp Kohlschreiber on Saturday, 6-3, 6-4, 6-4. Incredibly, it's the 15th consecutive year Federer has progressed to the fourth round.

He's won all nine of the sets he's played and is averaging just under seven lost games and 83 minutes per match. In fact, the total minutes he's been on court for three matches is one less than the 4-hour, 11 minutes that Marin Cilic needed Friday to win his third-round match.

"I think I won the big points today," Federer said in his on-court interview. "The difference in the match was only five points [80-75]. I served well at the end, even though it was a bit of an up-and-down match for us.

"It's good to get through in three sets, so I'm very pleased. They always say you can't win the tournament in the first week, but you can lose it."

Is it possible Federer is playing some of his best tennis -- ever?

"Yes," Federer said after his first-round match. "If I win the tournament here yes, maybe. Not if I win a first round, because these rounds are here to just keep on progressing and moving forward.

"I will take it match by match, of course. I'm not thinking too far ahead, as I know some people are."

The US Open has always been physically challenging for Federer, even though he's won it five times. These days, as the oldest man left in the draw, it's important for him to get off the court in early rounds and so far he's succeeded.

His first-round win over Leonardo Mayer consisted of five dropped games and a total of 77 minutes  -- which tied for the second-fastest men's match. His second-rounder over Steve Darcis saw him lose only four lost games and required 80 minutes, the fourth-fastest match. Saturday, it was 93 minutes -- not bad for an opponent like Kohlschreiber.

The 20 games he has lost in three matches equals his second-fewest in a Grand Slam during which he's played three full matches. In winning Wimbledon in 2004, Federer dropped 19 games in the first three matches.

The biggest reason for Federer's swift match times is his improved serve. Statistically, he's serving better than he ever has, believe it or not. When Kohlschreiber broke him to level the second set at 2-all, it ended an impressive streak of 78 consecutive service holds; Federer had gone nearly a month as a 34-year-old without a dropped service. Kohlschreiber broke Federer again early in the third.

In truth, the 31-year-old German was a tricky opponent for Federer. He came within two points of beating Federer for the first time back in Halle, before Wimbledon, and he has beaten American John Isner three straight years here in the third round.

Kohlschreiber is, nevertheless, 0-10 against Federer for his career.

Once again, Federer busted out his new shot, rushing the service line late in the second set and picking up a Kohlschreiber second serve with a sweet half volley. The ball nicked the netcord and Federer raised his hand in a pro forma act of courtesy -- and Kohlschreiber hung his head.

Federer still has an exquisite sense of timing. He was muddling along at 4-all, with Kohlschreiber serving at 30-love, when he suddenly won four straight points and found himself serving for the match.

And now, Federer meets the 6-foot-10 Isner in a Monday fourth-round match. Isner, typically among the ATP World Tour's ace leaders, is second here with 64, but he's played only eight sets, because of Jiri Vesely's retirement because of a neck injury.

"It's a tough match," Federer acknowledged. "John's gotten me good in Davis Cup. Clearly, he's one of the best servers in the game."

Will he try his crazy rush of net on Isner's serve, which has already been clocked here as high as 141 mph?

"I don't think so," Federer said. "I don't think he's the guy to try it"