Japan's Kei Nishikori caused the second major shock of the Madrid Open by knocking out defending champion Roger Federer in three sets, 6-4 1-6 6-2.
After world No 1 Novak Djokovic was surprisingly beaten by unseeded Bulgarian Grigor Dimitrov on Tuesday, not even Federer's eye-catching mint-green shirt could put his opponent off in the Magic Box arena.
World no 14 Nishikori showed tremendous composure to defeat the 31-year-old, who was playing his first tournament since losing to Rafael Nadal at the Indian Wells Masters in March.
Federer was broken in the fifth game of the first set as Nishikori went on to seal it comfortably 6-4, but the Swiss maestro seemed to have found his rhythm in the second as a double break saw him take the set 6-1.
However, Nishikori dominated the third set as he broke to go 2-1 in front and then again in the final game to move into the quarter-finals and a meeting against Spain's Pablo Andujar.
It was Nishikori's biggest win since he beat Serb Djokovic in the semi-finals in Basel in 2011. Meanwhile, defeat for Federer means he will lose his world No 2 ranking to Briton's Andy Murray.
"He started playing much better in the second set, but I started to keep the ball in the court and played a lot more aggressive and everything started going well for me after that," the 23-year-old Nishikori told Sky Sports.
Asked if this was the highlight of his career, he added: "Yeah, I think so. It's the biggest win for me and it's on clay which is not really my favourite surface. It's an amazing feeling."
Meanwhile, seventh seed Jo-Wilfred Tsonga needed three sets to overcome local favourite Fernando Verdasco 4-6, 6-3, 6-2. The Frenchman will face the winner of the tie between Stanislas Wawrinka or Djokovic's conqueror Dimitrov in the last eight.