Roger Federer's preparations for the French Open came to a shuddering halt after he was stunned by Japan's Kei Nishikori at the Madrid Open Thursday.
World No.2 Federer, who was playing his first tournament since losing to Rafael Nadal at Indian Wells in March, suffered a 6-4 1-6 6-2 third round defeat by the 14th seed.
The Swiss ace follows World No.1 Novak Djokovic in crashing out of the tournament with the Serb star losing to Bulgaria's Grigor Dimitrov on Tuesday
Federer, 31, has won 17 grand slam titles during his illustrious career, but has managed just one win at Roland Garros.
This defeat will see him slip down below Andy Murray to number three in the world and Federer admits his performance came as something as a surprise.
"Overall, I'm pretty disappointed with my play," he told a press conference following the match.
"I'm not sure how well Kei thought he played. I didn't think he had to play his very best either, which is even more disappointing.
"It doesn't change my mindset going forward. I'm going to go back to the practice court, train hard, and make sure I don't have these kind of days anymore."
But while the start of the French Open is less than three weeks away, Federer is adamant this latest setback will not affect his chances of glory at Roland Garros.
He told reporters: "We're not playing for the French Open. This is early. We're weeks away from the French Open.
"It's nice to have the French Open as a tournament on the calendar but not everything is sacrificed for that.
"For that particular player or for the media or the fans the French Open is the ultimate thing and the only thing they care about.
"Then clearly Madrid is the lead up tournament.
"That's not how I see it. For me, every tournament counts.
"So I'm as disappointed losing here as the French Open. There is no difference really."
But for Nishikori, who lost his only previous meeting in straight sets against Federer in Basel two years ago, this was possibly the greatest win of his career.
"He's my idol," the 23-year-old told reporters after seeing off Federer.
"Beating him was one of my career objectives.
"It's fantastic that this happened on a clay court. As you know, it's not my best surface."
"I lost second or third round last week and I was struggling a little bit so I didn't have much confidence.
"But I played two good matches in the first and second round and to beat Roger, well, I'll need a couple days to celebrate."
Nishikori will play Spanish qualifier Pablo Andujar for a place in the semifinal.
Meanwhile, Rafael Nadal is into the last eight after defeating Russia Mikhail Youzhny 6-2 6-3.
The World No.5, who lost out in the third round last year, has won four titles since his return to action in February following a seven-month injury layoff.
Nadal, who is hoping to win an eighth French Open crown in Paris, told Spanish television that he was happy with his current level of fitness.