LONDON — Top-ranked Serena Williams hasn't won a Grand Slam since Wimbledon a year ago, but the 21-time major champion appeared confident about her chances of retaining the title on the eve of the tournament.

“Honestly, I don't feel any pressure,” said Williams, keeping her answers short at a pre-tournament news conference Sunday. “I feel good and confident.”

Williams surprised many by failing to win any of the past three Grand Slam tournaments.

She fell to Roberta Vinci of Italy in the 2015 US Open semifinal, to Angelique Kerber of Germany in the 2016 Australian Open final and to Garbine Muguruza of Spain in the French Open final earlier this month.

Instead of bemoaning those losses, however, Williams prefers to focus on coming back stronger.

“I think it's important to learn from every loss that you have,” she said. “I think, in particular, throughout my whole career [I] have been able to learn a lot to come back a much better player.”

Williams enters Wimbledon maintaining her No. 1 ranking for what will be an impressive 300th week at the top.

Nevertheless, Muguruza, Kerber, Agnieszka Radwanska and Simona Halep are all positioned to oust Williams from the top spot by the end.

Williams will play 148th-ranked qualifier Amra Sadikovic of Switzerland, a player she admits knowing nothing about, in the first round on Tuesday.

“It doesn't matter who I play,” she said. “It doesn't matter to me.”

When she captured her sixth Wimbledon trophy last year it capped the second time in her career she held all four Grand Slam titles in a non-calendar year. She first achieved that distinction in 2002-03.

“It was a great accomplishment to win four Grand Slams in a row twice in my career,” Williams said. “It's pretty cool. It's really awesome.“

Like Williams, two-time defending champion Novak Djokovic arrived at Wimbledon without having played a grass-court tuneup tournament.

Where the two don't agree is in their attitude: Williams insists she feels no pressure to perform this fortnight, while Djokovic believes it's impossible to escape those expectations.

“It's always present. Pressure is part of what we do,” he said. “It's inevitable to face this kind of sensation as a top player, being expected to do well and to go as far as last four at least in the tournament, or finals.”

Djokovic starts his campaign for a fourth Wimbledon trophy by taking on British wild card James Ward in their first meeting.

As tradition dictates, Djokovic, as the men's defending champion, will open the Centre Court competition.

“It's going to be the first match on the untouched grass,” Djokovic said. “That's probably one of the most special tennis matches that you get to experience as a professional tennis player.”

Djokovic understands the emotions behind simultaneously holding all four Grand Slam titles, which he achieved when he won his first career French Open title earlier this month.

Last year, Williams had a chance to win a calendar Grand Slam, but fell short at the U.S. Open.

This year, Djokovic remains in contention to be the first man since Rod Laver in 1969 to achieve a calendar Grand Slam, since he has already won the Australian and French Opens.

Williams, for one, says Djokovic could be the player to get the deed done.

“He has every opportunity to do it,” she said. “I think he'll get it easy. So he should be fine.”