Sixth seed Andre Agassi crashed out to Finnish qualifier Jarkko Nieminen in the first round of the French Open after aggravating a back problem.
The 1999 champion was left hobbling around the court after winning the third set on a tie-break to lead 2-1.
The 35-year-old American, who was making his 17th and possibly last appearance at Roland Garros, eventually went down 7-5 4-6 6-7 6-1 6-0.
Nieminen, ranked 95th in the world, now faces Russia's Igor Andreev.
After his shock defeat, Agassi revealed he had received a cortisone injection in February to cure a long-standing back injury only for the problem to flare up again midway through the third set.
"The sciatic nerve in my back started to get inflamed and it sent pain down my right leg and it got worse by the minute," he said.
"It's a concern that needs to be addressed because it hurts. I had the injection and it worked for a while.
"I was close to shaking hands at the end of the third set, but I didn't want to walk off, I didn't want to finish that way."
Agassi said he has been told he can take up to three cortisone injections in a year and is facing the prospect of another one to see him through Wimbledon next month and the US Open in August.
"When I go home and walk just a couple of blocks, you wouldn't think I was a professional athlete," he said.
"When the weather's cold, it's a problem. When the temperature drops and the wind blows, I get stiff and the pain gets worse from the top of the right hip all the way to my ankle. There's no way of controlling it."
But he insisted that Tuesday's setback will not rush him into retirement.
"The injection takes 10 minutes and if I can get a few months of playing out of that, it's alright with me," he said.
"It's disappointing to feel like this, not to be competitive but I will keep plugging away until there's nothing I can do about it."
Nieminen said Tuesday's victory was the biggest of his career and made up for his loss to Agassi two years ago, when the American dropped just two games.
"I played him before and he destroyed me, but I had nothing to lose," said the 23-year-old Finn.
"I thought Andre might have been struggling in the last two sets because he had been trying to finish the points early.
"I had 5-0 in the final set but it's not easy to play mentally against Agassi. His career has been unbelieveable."