PARIS — Lleyton Hewitt lunged and whiffed at some serves, his racket hitting only air. He simply stood and watched other balls whirr past.

Over and over and over again today, Hewitt's opponent in the French Open's first round, the 6-foot-10 Ivo Karlovic, smacked aces from on high, finishing with a tournament-record 55. Those easy points helped Karlovic take the first two sets — and made Hewitt think back to the day in 2003 when he was the defending champion at Wimbledon and lost his opening match to the tallest player in tour history.

"The angle he gets, you can't touch a lot of his serves," Hewitt said. "It's physically impossible."

This time, as the 26th-seeded Karlovic tired in heat that topped 80 degrees, Hewitt grew more and more comfortable, and the two-time major champion's bothersome hip looked fine while he climbed all the way back for a 6-7 (1), 6-7 (4), 7-6 (4), 6-4, 6-3 victory.

How could a player who compiles 55 aces possibly lose?

"Don't know," was Hewitt's simple reply.

Karlovic was similarly befuddled, saying: "It is difficult to explain."

Theirs amounted to the most riveting match of Day 1 at the only Grand Slam tournament that starts on a Sunday. Otherwise, there were straight-set wins for defending champion Ana Ivanovic, Andy Murray and Marat Safin — who is appearing in his final French Open, but please be sure not to ask him about that — and straight-set exits for 2004 champion Gaston Gaudio and two-time major winner Amelie Mauresmo.

No. 16 Mauresmo and No. 19 Kaia Kanepi were the seeded women who lost, while Karlovic was the only seeded man who departed. No. 9 Victoria Azarenka and No. 11 Nadia Petrova — who beat Lauren Embree of Marco Island, Fla. — won, as did No. 7 Gilles Simon, No. 8 Fernando Verdasco, No. 13 Marin Cilic and No. 14 David Ferrer.

Safin is seeded 20th, and his talent and temperament long have conspired to make him as capable of reaching the semifinals at Roland Garros, something he did in 2002, as he is of falling in the first round, something he did in 2006.

He reached the second round this year by defeating Alexandre Sidorenko of France 6-4, 6-4, 6-4. When the 29-year-old brother of the tournament's top-seeded woman, Dinara Safina, walked off the court, he was asked by a French TV interviewer whether this is his last appearance at Roland Garros. Safin replied: "I'm tired of talking about this."

Pressed, he said: "Well, yeah, I decided, I think, to stop. I had my 12 years of my career. It was a great experience, but it's time to move on."

Like Safin, Hewitt has been ranked No. 1 and has won a U.S. Open title. Hewitt, who is a year younger, has given no indication he plans to walk away from the sport anytime soon.

He certainly never quit for a moment against Karlovic, even if the situation seemed grim. Hewitt had lost all three previous career matches against Karlovic, and faced that daunting two-set deficit Sunday. Then there were all of those aces: By the end of the third set, Karlovic already had 41 — enough to top the previous French Open record of 37, set by Andy Roddick in 2001.

The final tally of 55 is the most in a tour-level match since the ATP began keeping ace records in 1991, bettering the mark of 51 shared by Karlovic and Joachim Johansson. And, according to the book The Bud Collins History of Tennis, it's the second-most in history, behind only the 59 hit by Ed Kauder at the 1955 U.S. Championships.

Karlovic doesn't try to keep track of his aces during matches, and he only rarely consults stat sheets, so he wasn't aware of the significance of Sunday's performance.

"Oh, yeah? How many aces? 55? All right, at least a record. At least that," he said. "It is good. Obviously, even on the clay, I can serve unbelievable."

True enough. Hewitt is known as one of the game's top returners, and he called the matchup "sort of his strength against mine."

In the end, though, what really mattered was Hewitt's mental strength, while Karlovic wilted under the searing sun.

"It was like I had no energy," Karlovic said. "I could not run."

The temperature was cooler, and the light fading, by the time France's Mauresmo delivered her latest disappointing performance at home, a 6-4, 6-3 loss against Anna-Lena Groenefeld in the evening's final match.

"We couldn't see," Mauresmo said.

Hours earlier, Ivanovic got the tournament started on Court Philippe Chatrier, and she looked a bit shaky at the site of her only Grand Slam title.

With pieces of black tape on her troublesome right knee, she wasted 15 break points, fell behind 5-4 in the first set, and only for about a four-game stretch really asserted herself in a 7-6 (3), 6-3 struggle against 44th-ranked Sara Errani of Italy.

Errani, for one, was not impressed.

"Is she going to win the tournament?" Errani said. "Don't think so."