Four compelling quarterfinals highlighted play at the US Open on Wednesday, two on the men’s side and two among the women.

Nishikori Wins another Epic

In what turned into a highly competitive match, 10th seed Kei Nishikori defeated third seed Stan Wawrinka 3-6 7-5 7-6 (7) 6-7 (5) 6-4.

After a match that ended at 2:26 AM, less than 40 hours before the start of his quarterfinal match on Wednesday, it would have been understandable if Kei Nishikori came out sluggish. Early in the first set, it appeared as though the Japanese player may have struggled with lingering heavy legs from a match that tied the record for the latest finish to a U. S. Open night match. He fell 6-3 to Wawrinka, who had his own battle against Tommy Robredo two days ago.

However, in the second set, Nishikori appeared to quickly find his legs and capitalized on 19 unforced errors to even the match. Both players brought high-quality tennis to the table in the third. With his exuberant coach, Michael Chang, cheering him on, Nishikori traded crisp groundstrokes with Wawrinka. Both men produced strong backhands throughout the set. After each earned a break, the set advanced to a tiebreak. During a span in which each player found streaks of success, Nishikori outlasted the Australian Open champion at 9-7.

With both players protecting serve in the fourth, neither could make significant inroads toward a break. Perhaps conserving energy on returns while stepping up intensity on service games, they advanced to another tiebreak. This time, Wawrinka jumped out to a fast start, but once again Nishikori showed fight, battling back from 0-4. However, the Swiss champion found impressive winners at key points and took the tiebreak at 7-5.

In the deciding set, both players placed a high emphasis on service games, until the Japanese gained a 5-4 advantage in the set. With Wawrinka needing a service hold to stay in the match, Nishikori found two match points. And while Wawrinka was able to save one, Nishikori broke to take the match.

Nishikori had a successful day at the net, where he won 29 of 37 net approaches. He also benefited from 78 unforced errors by Wawrinka. For the second straight match, Nishikori battled for over four hours to earn the win.  With the victory, he became the first Japanese player to advance to the U. S. Open semifinals in 96 years.

Nishikori assessed his results courtside. “I started a little bit tight, but my body was ok. I got more confidence, especially in the third, and I don't know how I finished the game, but I’m very happy.”

Makarova Advances past Azarenka

The 17th-seeded Ekaterina Makarova advanced to her first Grand Slam semifinal behind a 6-4 6-2 victory against 16th seed Victoria Azarenka.

Azarenka has been slowed by injury in 2014 but has launched a comeback to her previous form, which has seen progress in New York. Early on, it appeared as though the Belarus native was on the right path as she broke the Russian early and appeared to have momentum on her side. However, Makarova quickly broke back and attacked Azarenka's serve once more and took the first set. Despite a poor serving set by Makarova, she found success attacking her opponent’s second serve, and the results were just enough to give her the advantage.

In the second, it was the Russian assaulting Azarenka's serve once more, finding even more success. The 25-year-old was only successful in placing 48 percent of her first serves in the set, and Makarova took advantage with four breaks of service. A frustrated Azarenka aggressively slammed her racket during the set, receiving a warning, but the act did not light a fire under the two-time Grand Slam champion. Instead, she lost her serve once more, which led to Makarova's victory as she rolled in the second set.

Afterwards, Azarenka kept it short and sweet, “Yes, I’m disappointed, but I feel like I tried my best with whatever I had. I just want to wish her good luck. That’s it. I’m out of the tournament,” she said.

Meanwhile, Makarova was pleased with the outcome, “I’m feeling amazing, finally I’m in a semifinal,” she said. “It’s a great feeling.” She will face Serena Williams in the semifinals.

Serena Rolls

Serena Williams is back into the semifinals of the U. S. Open after her 6-3 6-2 victory against Flavia Pennetta in just over an hour.

The 11th-seeded Pennetta admitted that she had nothing to lose entering her match against the world No. 1. She opened up the match very confidently as she broke Williams twice. However, the American finally warmed up, and the flood gates opened as Williams won the next six games to take the first set.

In the second set, Pennetta’s resistance stiffened early, but once again, Williams broke her serve to gain an advantage and never looked back.

Williams finished the match with 31 winners while breaking Pennetta's serve five times. She commented on her slow start after the match, “I don't feel like I was doing too much wrong,” she said. “So I said, 'If she keeps it up, she absolutely deserves the win.' And I just tried to do a little better.”

Djokovic Defeats Murray in Four

Two familiar rivals met in a quarterfinal match in Arthur Ashe Stadium. Top seed Novak Djokovic faced eighth seed Andy Murray and prevailed after a 7-6(1) 6-7(1) 6-2 6-4 battle.

Two-time Grand Slam champion Murray attacked a shaky Djokovic serve right out of the gate, recording a break. But the Wimbledon champion immediately returned the favor and fed off of his early success, gaining a 4-1 advantage. However, Murray fought back to get back on serve, and the two battled to a first-set tiebreak.

In the tiebreak, Djokovic jumped out to a fast start, which was too much for Murray to overcome, and the Serb took the tiebreak at 7-1 and the first set.

In the second set, with Murray serving in the third game, Djokovic capitalized on a poor service game by the 27-year-old, grabbing an early break once more. However, just as in the first set, Murray evened the set up after the frustrated Serb let him off the hook on his own service game. As play progressed, the intensity escalated as Djokovic served to force a tiebreak at 5-6. Murray, feeding off huge forehand strikes sent the Serb into defensive mode. But as quickly as Murray found a set point, Djokovic rallied with big strikes of his own and forced a second-set tiebreak.

In a polar opposite of the first-set tiebreak, Djokovic dug himself a hole with sloppy groundstrokes. And in a complete reversal of their first-set tiebreak, Murray took the second set with a 7-1 tiebreak win.

Murray went into the third set riding momentum, but the Serb picked up and steadied his game. He broke the Scot, who suddenly appeared to be fighting some fatigue. Djokovic maintained the pressure, breaking once more to take the third set.

In the fourth, like a shark with blood in the water, Djokovic sensed that Murray was fading. However, despite his early efforts, Djokovic could not break into an ailing Murray's serve, which appeared to be effected by a back problem. That injury took its toll as the set progressed, and as Murray served at 4-5, Djokovic broke serve, taking the set and match.

It is Djokovic's eighth consecutive trip to the U. S. Open semifinals. He will meet Kei Nishikori on Saturday.