Kevin Anderson's comeback from an injury-marred 2017 season skidded to at least a temporary halt on Monday as he was forced to retire from his Round of 16 French Open match against Croatia's Marin Cilic with a sore left hamstring.
The South African veteran lost the first set 6-3 as he struggled with his serve and managed just three winners. He retired trailing 0-3 in the second. It was the first time in Anderson's decade as a professional that he has pulled out of a match at a Grand Slam event.
Anderson (31) said his woes began in the first round and "progressively worsened" as he defeated 18th seed Nick Kyrgios of Australia in the second round and outlasted young British talent Kyle Edmund in five sets to advance to the fourth round - an effort he may have paid for on Monday.
"Tried the best we could today,'' Anderson said. "It just wasn't happening. The serve was not firing properly. I wasn't able to use my legs properly. As the match went on, movement became increasingly difficult.
"With the grass (season) just around the corner, I have to look after my body. And I've been through quite a bit. So hopefully right now I'll be able to recover rapidly.''
Still, Anderson said he will walk away from Paris encouraged, calling Monday "a hiccup" in his progress.
"I feel like there's been a huge improvement in the way I've been able to compete on the match court and the way I've performed,'' he said. "I feel like some of my matches have created a lot of chances. I haven't necessarily taken them as soon and as effectively as I would have liked to, but I think that's just a positive sign.''
Anderson, who achieved his career-high ranking of World No. 10 on 12 October 2015, will climb inside the top 40 when the new ATP rankings come out next week.