LONDON — For the second straight year, Rafael Nadal is leaving Wimbledon early after a stunning loss to a little-known player ranked in the hundreds.

In one of the tournament’s greatest upsets, an ailing Nadal was knocked out in straight sets Monday by 135th-ranked Steve Darcis of Belgium — the Spaniard’s first loss in the opening round of any Grand Slam event.

The free-swinging Darcis defeated the two-time champion 7-6 (4), 7-6 (8), 6-4 on Court 1, ending Nadal’s 22-match winning streak and eliminating one of the Big Four of men’s tennis on the very first day of the grass-court Grand Slam.

After serving an ace down the middle on match point, Darcis conceded he was as surprised as everyone.

“Nobody was expecting me to win,” he said. “So I had to play a good match, relax, and enjoy the game. That’s what I did.”

There were no surprises for the other big names: Defending champion Roger Federer, bidding for a record eighth Wimbledon title, and second-seeded Andy Murray both won in straight sets on Centre Court.

Nadal was sidelined for seven months with a left knee injury after losing in the second round of Wimbledon last year. He seemed to be struggling physically Monday. He was unable to turn on the speed or use his legs to spring into his groundstrokes, limping and failing to run for some shots.

Nadal declined to blame any injury and gave full credit to the 29-year-old Darcis, who had never beaten a top-5 player before and has yet to go beyond the third round of any Grand Slam.

“I don’t … talk about my knee this afternoon,” Nadal said. “Only thing that can say today is congratulate Steve Darcis. He played a fantastic match. Everything that I will say today about my knee is an excuse, and I don’t like to put any excuse when I’m losing a match like I lost today.”

Darcis, who had won only one previous match at Wimbledon, played the match of his life Monday, going for his shots and moving Nadal from corner to corner. Darcis amassed a total of 53 winners, compared with 32 for Nadal.

“Of course, Rafa didn’t play his best tennis,” Darcis said. “I could see it. So I took advantage of it, tried to fight. Maybe he was not in the best shape ever. Maybe he didn’t play his best match. But I have to be proud of me, I think.”

Darcis said he didn’t know whether Nadal was injured, or was just troubled by the grass conditions.

“Not the day to talk about these kind of things,” Nadal said. “I am confident that I will have a good recovery and be ready for the next tournaments.”

Darcis finished the match in style, serving his 13th ace as Nadal failed to chase the ball.

Darcis is the lowest ranked player to beat Nadal at any tournament since Joachim Johansson — ranked No. 690 — defeated the Spaniard in 2006 in Stockholm. Gustavo Kuerten, in 1997, was the last reigning French Open champion to lose in the first round at Wimbledon.

Nadal was coming off his eighth championship at the French Open this month. But on this day he never looked like the player who has won 12 Grand Slam titles and established himself as one of the greatest players of his generation.

Last year, Nadal was ousted in the second round by 100th-ranked Lukas Rosol, a match that finished under the closed roof of Centre Court.

After that loss, Nadal took the rest of the year off to recover from the knee problem, missing the U.S. Open and Australian Open. Since returning to action this year, he had made it to the finals of all nine tournaments he entered, winning seven.

After winning the French Open, Nadal pulled out of a grass-court tuneup in Halle, Germany. He came to Wimbledon without any serious grass-court preparation.

“The opponent played well,” Nadal said. “I had my chances. I didn’t make it. So in grass (it’s) difficult to adapt yourself, to adapt your game. When you don’t have the chance to play before, I didn’t have that chance this year, is tougher. I didn’t find my rhythm.”

Ten years after his first Wimbledon championship, Federer opened play on Centre Court as defending champion and looked right as home as he dismantled Victor Hanescu of Romania 6-3, 6-2, 6-0.

This was a grass-court clinic lasting 68 minutes. Federer had 32 winners, seven aces and just six unforced errors. He won 90 percent of the points when he put his first serve in. When his serve is clicking, Federer usually is unbeatable. On this day, he won his first 15 service points and 24 out of the first 25.

“I’m happy to get out of there early and quickly,” Federer said. “So it was a perfect day.”

Last year, Federer equaled Pete Sampras and William Renshaw with seven Wimbledon titles. He is now contending to become the first man to win the tournament eight times, which would bring his total of Grand Slam titles to 18.

Federer came out wearing a white collared jacket with orange trim, then quickly got down to business. He never faced a break point and broke six times.

Federer has a habit of making things look easy. And so it was in the opening game when, stranded at the net, he reached behind him for a reflex forehand volley that landed in for a winner. In the third set, Federer lifted a perfect backhand lob over the 6-foot-6 Hanescu for a break and a 5-0 lead.

Murray, the U.S. Open champion who again tries to become the first British man to win the trophy since Fred Perry in 1936, got off to a strong start with a 6-4, 6-3, 6-2 win over Benjamin Becker of Germany.

“It was a tough start for me. He is a very good grass player,” Murray said. “I was ready and to win in three sets was a good start. There’s always nerves at the start of a Grand Slam and I’m glad to get it out of the way and hopefully I can improve as it goes on.”

It was Murray’s first match on Centre Court since he beat Federer on the grass for the gold medal at last year’s London Olympics — a month after losing to Federer in the Wimbledon final. The two could meet in the semifinals this year.

The weather was mostly cloudy but dry for the beginning of the two-week championships. Among those in the Royal Box were former U.S. Secretary of State Condoleeza Rice and Pippa Middleton, the younger sister of Prince William’s wife, Kate.

In women’s play, there was an early upset as fifth-seeded Sara Errani was eliminated by Puerto Rican teenager Monica Puig 6-3, 6-2.

Puig slugged 38 winners in overwhelming Errani in the first match on Court 18. The 19-year-old Puig, playing her first grass-court tournament as a pro, completely outplayed the Italian veteran with her hard-hitting baseline game.

Puig said she has been building on a recent run of success, including a third-round showing at the French Open.

“Definitely pulling off some big career wins and not being afraid to close out matches, which was my problem at the beginning of the year,” she said. “Finally just having the confidence to close them out.”

In other women’s matches, second-seeded Victoria Azarenka overcame a right knee injury from a scary fall beating Maria Joao Koehler of Portugal 6-1, 6-2.

Azarenka screamed in pain after slipping and falling at the baseline in the second game of the second set. She sobbed on court and received medical treatment.

Playing the rest of the match with a heavy wrap on her right knee, Azarenka limped noticeably but managed to win comfortably against an opponent making her Wimbledon debut.

“I was in such pain at the beginning, it wouldn’t let go,” Azarenka said. “I think it calmed down.”

Third-seeded Maria Sharapova, the 2004 Wimbledon champion, came through a first-set tiebreaker and beat 37th-ranked Kristina Mladenovic of France 7-6 (5), 6-3.

Sharapova drew attention over the weekend by delivering a sharp news-conference rebuke to Serena Williams over critical comments attributed to the top-seeded American in a recent magazine article. Sharapova swatted away questions about the feud Monday.

“I’ve said everything that I wanted to say about the issue,” she said. “Wimbledon started. This is my work. This is my job. I’d really appreciate it if we move on.”

Other women’s winners Monday included No. 9 Caroline Wozniacki, No. 12 Ana Ivanovic and No. 16 Jelena Jankovic.

Advancing among the men were No. 6 Jo-Wilfried Tsonga, No. 10 Marin Cilic, No. 15 Nicolas Almagro and No. 18 John Isner. Janko Tiparevic, seeded No. 14, lost to fellow Serb Viktor Troicki, 6-3, 6-4, 7-6 (5).