Britain's Jack Draper had to retire from his fourth-round match with Carlos Alcaraz at Indian Wells because of a stomach muscle injury.

His serve speed started to drop late in the first set and he shook hands with Alcaraz after just 46 minutes on court.

"I was doing further damage, so there was no point in making it worse," the 21-year-old told BBC Sport.

"At the end of my match against Andy [Murray, on Monday], I obviously had a bit of hip pain but my ab towards the end was getting sorer.

"I woke up [on Tuesday] and my ab was sore and when I started serving 100% in the match it gradually got worse. I couldn't really play properly."

Alcaraz had been on top in the early stages. Taking the ball early and playing with explosive pace, he won the first set 6-2

Draper did have his chances. After dropping serve in the opening game, he had 0-40 in the next game, but the Spaniard saved all three break points and the tone of the match was set.

Draper suffered a series of retirements in 2021, but was able to play 22 events last year. His only retirement, because of a groin injury, came in a US Open third-round match against Karen Khachanov.

His body is still not robust enough, but he has invested in the services of Dejan Vojnovic, a former Olympic sprinter who travels regularly as his fitness trainer.

"I'm at the start of properly working hard on my fitness training," Draper said.

"I've done a lot of stuff on court over the years but I've never really worked truly on my body.

"I'm still early in my development. I'm starting to play Grand Slams with five sets. The physical nature of this sport is very demanding and so you've got to have a really resilient body to cope with the demands of the tour.

"My tennis is right there. It's just this body aspect which is going to take a bit of time and that is just something I'm going to have to accept."

Draper, who was unable to play between the Australian Open and Indian Wells, now faces another spell on the sidelines and will have a scan later on Wednesday to learn the extent of the injury.

Alcaraz, meanwhile, is now just three wins away from replacing Novak Djokovic as the world number one.