Rafael Nadal has yet to lose his serve through five matches at the U.S. Open. (Ray Stubblebine/Reuters)

This time last year, Rafael Nadal watched the U.S. Open on television, exiled from the tournament he won in 2010 by a flare-up of tendinitis in his knees.

The timetable for Nadal’s return was unclear, as was the weightier question of whether the former No. 1 would recover to the point of being able to contest major titles in the future.

But since his return to competition in February following a seven-month hiatus, Nadal has won nine titles (more than any player on tour); compiled a 58-3 match record that includes a 20-0 mark on hard courts; and stormed into Saturday’s U.S. Open semifinals with scarcely a hiccup, yet to lose his serve through five matches.

While Richard Gasquet, the opponent who awaits, is widely regarded as one of the more naturally gifted players on tour, the 27-year-old Frenchman is 0-10 against the Spaniard.

The two last met in a 2011 Davis Cup match, with Nadal delivering a straight-sets rout on clay. Gasquet last won a single set against Nadal in 2008, and even that was a squeaker, with Gasquet eking out a 14-12 tiebreak.

Few men have had much chance against Nadal, who holds a winning record against every seeded player at this year’s U.S. Open.

His advantage isn’t the result of freakish gifts; rather, exceptional attention to detail in his quest to become a better, more complete player. Nadal is highly self-critical without being self-defeating, reviewing each performance, victories included, for any weakness that needs shoring up.

And he takes nothing for granted, refusing to be lulled into thinking that past-performance guarantees anything despite his 12 Grand Slam titles.

Nadal approaches each opponent as if dangerous, regardless of their ranking, typically using the opening set of a match to feel out his adversary’s strengths and potential vulnerabilities. Only then, a few games into the contest, does he raise the stakes in a carefully calibrated manner — stepping in closer to return serve, increasing the pace and spin of his groundstrokes and seizing opportunities to charge the net.

In most cases, opponents who might have felt they had a chance against him at the outset find themselves mentally spent and physically depleted as the match grinds on.

“Nothing to say,” a stunned Tommy Robredo offered after getting pummeled by Nadal, 6-0, 6-2, 6-2, in their quarterfinal Wednesday.

Robredo, 31, was clearly uncomfortable in the cavernous surroundings on Arthur Ashe Stadium, where the wind swirls with maddening unpredictability.

“He was hitting the ball all the time very good, and I wasn’t able to get into the rhythm,” said Robredo, whose record against Nadal dropped to 0-7. “I wanted to start a little bit close in the score, and then we’ll see if I could play my best. But very soon he was up a break and he was hitting very, very fast and with a lot of confidence.

“Sometimes there is nothing to say. It’s just, congratulate the other, and hopefully next time we will have a chance.”