LONDON -- Back in her comfort zone on Wimbledon's Centre Court, Serena Williams delivered a statement that no one can argue with: When her powerful serve is clicking, she's still the woman to beat at the All England Club.

Putting aside her recent comments that led to a couple of apologies and a brief spat with Maria Sharapova, Williams looked every bit the five-time champion as she began her Wimbledon title defence with a routine 6-1, 6-3 victory over Mandy Minella of Luxembourg.

"For me, it's the greatest moment for a tennis player, to walk out on Centre Court," Williams said after her first match at Wimbledon since winning Olympic gold here last year. "That was such a great moment too. So many great memories on this court."

Top-ranked Novak Djokovic also opened his campaign with a straight-sets victory, beating Florian Mayer of Germany 6-3, 7-5, 6-4. Mayer is a two-time Wimbledon quarterfinalist -- losing to Djokovic at that stage last year -- but never looked like causing another major upset a day after Rafael Nadal's stunning first-round exit.

Djokovic took a 3-0 lead in the first set and broke for a 6-5 lead in the second to take firm control. He served out the match to love before saluting the Centre Court crowd with a fist pump.

"It was a big pleasure again performing here on Centre Court in front of the packed crowd," Djokovic said. "For the first round, it was tricky. ... I think (Mayer's) game is really well suited for grass, so it took a lot of effort."

For Williams, this was a chance to put the focus firmly back on tennis following the recent verbal jousting with Sharapova over their private lives -- and comments about a high-profile rape case that she had to apologize for -- and the American took full advantage.

As usual on grass, the top-ranked Williams dominated with her hard serve, winning the first set without dropping a single point on her service game. Her main weapon let her down only at the start of the second set, when Minella was able to take a 2-0 lead when Williams double-faulted on break point.

She was one point from going down 3-0 but then won 15 of the next 18 points to take a 4-2 lead, and broke again to wrap up the win.

But even her minor lapse at the start of the second set was enough to leave Williams a bit unhappy.

"I feel like I was a little rusty for some reason today," she said. "I don't feel like I played my best. I felt really upset when I lost my serve in the second set. With that being said, I think Mandy played really well."

Much of the pre-tournament talk was about Williams and Sharapova, the two top players in the game who are on opposite sides of the draw and can't meet before the final.

"It hasn't been a distraction. Like I said, I'm just here to focus on the tennis," Williams said. "I'm just here to play Wimbledon. It's the premiere tournament in the world, of the year, so that's what's most important."

Williams improved her career record to 68-8 at the All England Club and extended her career-best winning streak to 32 matches, which included her second French Open title.

Also Tuesday, 42-year-old Japanese veteran Kimiko Date-Krumm had an even easier time getting past an opponent, German teenager Carina Witthoeft, less than half her age, 6-0, 6-2 in just 44 minutes.

Date-Krumm is the second oldest player to have won a match at Wimbledon after Martina Navratilova, who was 47 when she reached the second round in 2004. The 18-year-old Witthoeft was making her Grand Slam debut.

Sixth-seeded Li Na of China also cruised into the second round, beating Michaella Krajicek of the Netherlands 6-1, 6-1.

Nadal, a two-time Wimbledon champion, was knocked out in straight sets by 135th-ranked Steve Darcis of Belgium on Monday -- the Spaniard's first loss in the opening round of any Grand Slam event.

On Tuesday, the only top player with any sort of difficulty advancing was French Open runner-up David Ferrer, who overcame a second-set slump and a scary late fall to beat Martin Alund of Argentina 6-1, 4-6, 7-5, 6-2.

Coming off his first Grand Slam final, the fourth-seeded Spaniard looked in danger of following Nadal out of the tournament as Alund won the second set and pushed hard in the third. But Ferrer broke for a 6-5 lead and then went 5-1 up in the fourth. He had an injury scare at 3-1, however, when he fell to the ground and grimaced in pain after his left foot slid backward awkwardly on the grass. Ferrer eventually got back up, and went on to break Alund's serve again.

He served out the match with an ace, and said afterward that his foot was "fine."

Most other matches on Tuesday also went according to plan.

Eighth-seeded Juan Martin Del Potro made a winning return to Grand Slam competition on Tuesday, defeating Albert Ramos of Spain 6-2, 7-5, 6-1 after sitting out the French Open because of respiratory problems. No. 12 Kei Nishikori of Japan and No. 13 Tommy Haas of Germany both won in straight sets, but 16th-seeded Philipp Kohlschreiber of Germany wasted a two-set lead against Ivan Dodig of Croatia and then had to retire in the fifth, saying he had a bout of flu.

Home favourite Laura Robson delivered the biggest upset, beating 10th-seeded Maria Kirilenko 6-3, 6-4 to become the first British woman to beat a top-10 ranked opponent at Wimbledon in 15 years.

"It was nerve-wracking before I served for it," Robson said. "I just wanted to focus and take it point by point. Any big win gives you a lot of confidence."