Paris ? It’s newsworthy enough when anyone manages to win a set against Rafael Nadal at any stage of the French Open — let alone two sets in the first round.

So a buzz built at Roland Garros on Tuesday when unseeded American John Isner pulled ahead of five-time champion Nadal by unfurling his 6-foot-9 frame to pound serves at upward of 140 mph, pushing up to the net time after time for volleys, and generally making the Spaniard uncomfortable for stretches.

“Quite clearly,” Nadal acknowledged later, “this is a match that I could have lost.”

In the end, he did not. Stretched to five sets for the first time in 40 career French Open matches, Nadal came back to emerge with a 6-4, 6-7 (2), 6-7 (2), 6-2, 6-4 victory over Isner and reach the second round.

“Really, what it came down to is the way he played in the fourth and fifth sets,” Isner said. “I haven’t seen tennis like that, ever.”

It was the most riveting match of a day that featured reigning U.S. Open and Australian Open champion Kim Clijsters’ first appearance at the French Open since 2006, a 6-2, 6-3 victory over Anastasiya Yakimova. Also advancing were Maria Sharapova, Li Na, Andy Murray, Robin Soderling and Sam Querrey.

Two seeded women lost: No. 20 Ana Ivanovic, the 2008 champion, was eliminated, 7-6 (3), 0-6, 6-2, by Johanna Larsson of Sweden, while No. 22 Dominika Cibulkova of Slovakia was beaten, 6-7 (10), 6-3, 6-2, by Vania King of the United States. No. 11 Nicolas Almagro departed with a five-set loss to Lukasz Kubot of Poland.

Nadal’s bid to tie Bjorn Borg’s record of six championships at the clay-court Grand Slam tournament nearly came to a too-abrupt-to-believe halt.

Consider:

• Nadal entered the day 38-1 at the French Open, his only loss coming to two-time finalist Soderling in the fourth round in 2009.

• Isner’s career in Paris before Tuesday? One first-round exit and one trip to the third round, for a 2-2 record.

• Nadal is ranked No. 1 and owns nine Grand Slam titles.

• Isner is ranked 39th and never has been past the fourth at a major tournament. He’s best known to date for winning the longest match in tennis history, 70-68 in the fifth set at Wimbledon last year, and setting a record with 113 aces in that marathon.

• Until the first of Tuesday’s two tiebreakers, Nadal hadn’t lost a single set at the French Open since 2009. And he hadn’t lost a set in any of 12 previous first- or second-round matches in the tournament.

So all seemed rather ho-hum when Nadal was leading Isner by a set and a break at 4-2 in the second. But Isner broke back to 4-all when Nadal missed a forehand, and suddenly, a tight match ensued.

“That’s when I started to sort of believe a little bit more,” Isner said, “and started to play with more confidence and strut around more out there.”

Even Nadal was a bit worried. So was Toni Nadal, Rafael’s coach and uncle, who would later say that from his perch in the stands he felt “very, very nervous, because losing in the first round is not too good for us.”

But his nephew steeled himself, and made zero — yes, that’s right, zero — unforced errors in the fourth set, while Isner made 12. Nadal broke Isner for a 2-1 edge in the fourth set, and called that “the turning point.”

Isner’s coach, Craig Boynton, agreed.

“Rafa getting up an early break in the fourth really helped his psyche,” Boynton said.

Nadal broke for a 2-1 lead in the fifth set, too, thanks in part to a cross-court backhand return winner, a forehand return winner, and a backhand return at the feet of the net-charging Isner.