Defending Wimbledon champion Elena Rybakina recovered from a nervous start to avoid a first-round exit against American Shelby Rogers.

She later put her nerves down partly to being the champion and also down to the presence of eight-time men's winner Roger Federer in the Royal Box.

However, last year's runner-up Ons Jabeur and second seed Aryna Sabalenka swept through with straight-sets wins.

Rybakina's win means she avoided becoming the first women's defending champion since 1994 to lose at this stage.

Steffi Graf was the champion who fell at that hurdle 29 years ago when she was beaten by American Lori McNeil - and after an error-strewn first set it had looked as if Rybakina would be joining the German in the history books.

But watched from Centre Court's Royal Box by both tennis royalty and actual royalty in the shape of Federer and the Princess of Wales, the Moscow-born 24-year-old battled to hold on to her own crown a little longer.

"Maybe that's why I was nervous because actually I really like Roger," Rybakina told a news conference.

"When I was younger, I was always watching him play."

Hampered by illness in her build-up to the grass-court Grand Slam, Rybakina got off to a shaky start, dropping serve in the opening game and serving two double faults in her first two service games, and she struggled to recover as a composed Rogers went on to seal the first set with an ace.

But, in a dramatic shift of momentum, it was soon the Kazakh who held all the aces, delivering five of them in a dominant second set that she whizzed through in 29 minutes as rain hammered down on the court's closed roof.

She broke in the opening game of the third set when a wide-looking forehand was shown to be in by Hawk-Eye, and maintained the advantage, wrapping up victory when world number 49 Rogers could only net a return.

Rybakina, who started her Wimbledon campaign last year on court 11, said it had taken her some time to adjust to being back on the stage where she won her maiden Grand Slam title.

"The double fault said it all at the beginning of the match," she said. "This is unusual for me.

"Here it's different. Straightaway you go to this big court.

"I think for me it's now a new chapter and this is something I need to get used and try to maintain my level."

She will play France's Alize Cornet or Japan's Nao Hibino in the second round as she bids to become the first woman since Serena Williams in 2016 to defend the women's singles title here.

'I didn't realise how much I missed Wimbledon' - Sabalenka

Belarusian Sabalenka, returning to Wimbledon after missing the 2022 championships because of a ban on players from her country and Russia, provided entertainment later on Centre Court with her heavy hitting and pinpoint accurate serving.

Sabalenka was in ruthless form as she swept to a 6-3 6-1 victory against Hungarian Panna Udvardy, ranked 82nd in the world.

"I didn't realise how much I missed this place until this match - I think that's why I played my best tennis today," said Sabalenka after the win.

The world number two said she could not watch the championships last year as it was too painful that she was missing out.

"I really love Wimbledon. I have great memories from two years ago. I made the semi-finals," she said. "It was a really tough period for me last year - I was just super happy to be here this year."

The Australian Open champion has been picked as many people's favourite for the championships and based on this performance few would argue against that.

"I feel great. I'm feeling good, it's really good being one of the favourites in this beautiful tournament," she said.

Jabeur 'pretends to be Ronaldo'

Returning to the tournament where Rybakina beat her to the title, Jabeur joked her week had started badly when she arrived and saw a photo on the wall of the Kazakh with the trophy in the locker room.

But sixth seed Jabeur opened her campaign with a no-nonsense 6-3 6-3 victory over Poland's Magdalena Frech, set to the backdrop of more rain hammering down on Court One's roof.

Despite having struggled with a calf injury for much of the season, the Tunisian was never really troubled by 70th-ranked Frech and even showcased some of her signature trick shots.

A stunning backhand volley leaping through the air and some lovely floated drop shots entertained the crowd as Jabeur joked after that she likes to pretend to be Cristiano Ronaldo on court.

"I played a lot of football when I grew up on grass, not tennis. I love football so much so maybe that's why I pretend I am Ronaldo playing here," she said.

"I like to joke around, I hate routine, doing those shots doesn't go to the basic forehand or backhand. I like to entertain the crowd, so hopefully I did that."