* Williams wakes up from first set slumber
* Nishikori first Japanese slam semi-finalist in 81 years (Adds Williams match)
By Larry Fine
NEW YORK, Sept 3 (Reuters) - Serena Williams and Ekaterina Makarova sprinted into the semi-finals of the U.S. Open on Wednesday but marathon man Kei Nishikori had to go the distance to upset Stan Wawrinka and become the first Japanese man into the last four of a grand slam in 81 years.
On a sultry evening, Williams sleepwalked through the start of her quarter-final with Flavia Pennetta as the 12th seeded Italian broke twice on the way to a shock 3-0 lead.
But the world number one, bidding for a sixth U.S. Open title and third in succession, woke from her slumber, storming through the next six games and romping to a 6-3 6-2 win.
Determined to make up for a disappointing season in which she failed to reach the quarter-finals in any of the three previous majors, Williams broke her fellow 32-year-old in the fifth and seventh games to advance in 63 minutes.
“It feels so special to be back in the semi-finals for the first time this year,” Williams, yet to lose more than three games in any set this championship, told the Arthur Ashe Stadium crowd.
“It’s an unbelievable feeling. I‘m so happy to have done it here.”
Russian left-hander Makarova made her best mark in grand slam singles by outslugging Victoria Azarenka, the U.S. Open runner-up the last two years, 6-4 6-2 in a snappy 87 minutes.
Tenth-seeded Nishikori registered his second consecutive upset by edging Australian Open champion Wawrinka 3-6 7-5 7-6 (7) 6-7 (5) 6-4 and was again made to work hard.
Having already played the longest match of the tournament in the fourth round, a bruising four-hour 19-minute battle with Canadian Milos Raonic, Nishikori had enough left in the tank to get past the Swiss third seed in a four-hour 15-minute test of wills.
“I don’t know how I finished the game, but I‘m happy,” an exhausted Nishikori, who had a medical timeout in the third set to have his right foot taped, told the Arthur Ashe Stadium crowd.
“I feel amazing. I‘m very happy to come to my first semis. I hope I can recover again and hopefully I can play 100 percent tennis next round.”
Nishikori will meet the winner of the evening session’s quarter-final between top seed and Wimbledon champion Novak Djokovic and eighth seed Andy Murray, the 2012 U.S. Open winner.
Seventeenth seed Makarova proved steadier and more explosive with her groundstrokes in dismissing Azarenka and reached the last four of a major for the first time after four losses at the quarter-finals.
Boldly going for winners at every opportunity against the former world number one, Makarova pressured Azarenka to a dozen break points and cashed in twice in each set for her victory.
“Finally I‘m in a semi-finals, finally I‘m here,” gushed the 26-year-old Makarova at Arthur Ashe Stadium.
“It’s a great feeling.”
Makarova has hoisted major trophies but always as part of a partnership, as winner of the French Open doubles in 2013 with Elena Vesnina and in mixed doubles at the 2012 U.S. Open with Brazilian Bruno Soares.
The Russian, however, has thrived on her own racket at Flushing Meadows, advancing without the loss of a set and dumping seventh seed Eugenie Bouchard in the process. (Additional reporting by Steve Keating; Editing by Frank Pingue / Ian Ransom)