Rafael Nadal's 30-match winning streak ended when the world number one was upset 7-6, 6-4 by fellow Spaniard David Ferrer in the Monte Carlo Masters quarter-finals.
Sixth seed Ferrer, who had beaten Nadal on clay only once 10 years ago and was brushed aside by the muscular left-hander in the French Open final last year, relied on his devastating forehand to prevail in over two hours.
Nadal, who made an uncharacteristic string of unforced errors, was looking to recapture his Monte Carlo crown after Serb Novak Djokovic had ended his eight-year reign in last year's final - his last defeat on the slow surface.
Ferrer will next face world number three and Australian Open champion Stanislas Wawrinka, who dismissed Canadian eighth seed Milos Raonic 7-6, 6-2.
"I have had to wait 10 years to beat him on clay. It was a long wait but I am pleased with the win and the way I played," Ferrer told Spanish TV.
"I spoke with my coach and we had a clear gameplan but with Rafa it's always tough because he doesn't allow you to follow it. The good thing was I was able to deal with his attacks and stay strong physically for the whole match."