By Mario Sarmento

Two days, two upset victories.

After knocking out fourth seed David Ferrer in a three-set thriller where he fought off four match points the previous day, No. 20 Kei Nishikori one-upped himself Wednesday night on Stadium Court, stunning two-time champion and No. 5 seed Roger Federer, 3-6, 7-5, 6-4 in the 2014 Sony Open Tennis tournament quarterfinals.

Federer, who had won all 27 of his service games and had lost just 18 points on serve in the entire tournament, was broken five times by Nishikori, all in the final two sets. “I’m feeling good,” Nishikori said. “To beat two top-10 players is big for me.”

After each player won his first four games on serve in the third set, Nishikori held to take a 5-4 lead. He immediately won the first three points of the final game, then watched as Federer hit a crosscourt forehand winner, and followed it with an ace. But Nishikori tracked Federer’s next serve, and hit a thundering backhand crosscourt winner to cap the shocking upset. “I played well, especially in the third. I was hitting both deep and striking well. Everything was going well,” he said. “You know there were a couple of tough moments, but I was fighting through and happy to win today.”

It was the same formula Nishikori had used to win the second set, as each player traded wins before the Japanese player served an ace to go up 6-5. With the next game even at 30-all on Federer’s serve, Nishikori hit a backhand winner, and the all-time Swiss great netted a backhand on the next point to win the set.

It didn’t look like the match would go the distance after the first set, which Federer won easily in just 34 minutes while breaking Nishikori twice. But Nishikori found his bearings, and he put pressure on the 17-time Grand Slam winner all night. Maybe Nishikori’s familiarity with Federer was the key to the upset, as Federer said prior to the match that the two used to be practice partners, and in fact, Nishikori had already beaten the Swiss player once in Madrid last year, also in three sets, to improve to 1-1 all-time against him.

The classy Federer complimented Nishikori on staying with his game despite falling behind. “He right away made me feel uncomfortable and stayed with me, so he was more consistent in the second and third, and those are the ones he won. At the end it’s his credit, of course,” he said.

Nishikori now reaches his second ATP World Tour Masters 1000 semifinal, against No. 2 seed Novak Djokovic, who beat No. 6 and defending Sony Open champion Andy Murray in straight sets earlier in the day. This is the furthest Nishikori has advanced in five appearances in Miami. “I played him a long time ago, maybe three or four years ago, you know, I beat him before, so hopefully I can play good like today,” Nishikori said of Djokovic.

In men’s doubles quarterfinals, wild cards Ryan Harrison and Jack Sock continued their run through the draw with a 6-4, 7-6 (4) victory over sixth-seeded Daniel Nestor and Nenad Zimonjic to reach the semifinals. Their opponents will be Colombians Juan Sebastian Cabal and Robert Farah, who upset the No. 2 seeds, Alexander Peya and Bruno Soares, 6-2, 7-6(4).

In women’s doubles, No. 5 Cara Black and Sania Mirza beat No. 4 Kveta Peschke and Katarina Srebotnik to advance to the semifinals, where they will play Martina Hingis and Sabine Lisicki.