London - Serena Williams begins her bid for a seventh Wimbledon title and record-equalling 22nd Grand Slam crown on Tuesday against a player who was once so disillusioned by tennis that she quit.
World number one and top seed Williams won her 21st major at the All England Club 12 months ago by beating Garbine Muguruza.
But the 34-year-old's hopes of going level with Steffi Graf's Open era record of 22 has stalled since that day.
She went down to a US Open semi-final loss to Italy's Roberta Vinci followed by defeat in the Australian Open final to Angelique Kerber and then to Muguruza in the French Open final earlier this month.
"It was a great accomplishment to win four Grand Slams in a row twice in my career. It's pretty cool," said Williams.
"This year I don't feel as much tension as I usually do."
Her opponent on Tuesday is Swiss qualifier Amra Sadikovic, a Macedonian-born world number 148 who quit tennis in 2014 to work as a coach.
Persuaded to return to the game, she has now qualified for a major for the first time.
"I worked with kids, adults, good juniors at a club in Basel. It was so much fun. It's something that I really want to do later on again," she said.
"But after a while I started missing competition. When you turn on the TV and you see the players playing the Grand Slams and you've beaten them, that hurts."
Second up on Centre Court is Andy Murray, the world number two and 2013 champion who tackles compatriot Liam Broady.
Murray has lost the Australian and French Open finals to Novak Djokovic this year and has since rehired Ivan Lendl as coach.
The two worked together when the British world number two won Wimbledon in 2013 and the US Open the year before.
They celebrated their renewed partnership with Murray claiming a record fifth Queen's Club title on the eve of Wimbledon.
"The last weeks have gone extremely well," Murray said.
"I don't feel any added pressure working with him again.
"It actually give a bit of extra confidence because I know last time we worked together, it was very successful. I trust in what he says.
Broady, 22, is ranked 234 in the world. He has won just one match on the main tour in his career and that was at last year's Wimbledon.
Also in first round action Tuesday are fourth seed Stan Wawrinka, who has hired 1996 Wimbledon champion Richard Krajicek to work with him.
Wawrinka faces American 18-year-old Taylor Fritz, the youngest player in the men's draw.
Two-time champion Petra Kvitova, the 10th seeded Czech, faces injury-plagued Sorana Cirstea of Romania.
Combustible Australian duo Nick Kyrgios and Bernard Tomic are in action on Court Two.
Kyrgios, the 15th seed and regarded as a dark horse for the title, faces 37-year-old Radek Stepanek, the oldest man in the draw.
Tomic, seeded 19, plays experienced Fernando Verdasco of Spain.
Former runner-up Agnieszka Radwanska of Poland, the third seed, faces Ukraine's Kateryna Kozlova.
Juan Martin Del Potro, the former US Open champion meets France's Stephane Robert.