Andy Murray’s hopes of back-to-back grand slam titles went up in smoke as Kei Nishikori twice came from behind to knock the second seed out of the US Open.
British number one Murray held a 2-1 lead over his Japanese opponent but the Scot let frustration get the better of him after an argument with the umpire, losing the next five games in a row as Nishikori pushed the match into a decider.
Nishikori seemed to let nerves get the better of him leading 4-3 as he squandered a 40-0 to allow Murray to break in the fifth set, but the Japanese player broke for a third time in the set at 5-5 before serving for the match to claim a shock 1-6 6-4 4-6 6-1 7-5 victory.
Two-time grand slam winner Stan Wawrinka set up a semi-final with Nishikori as he ended Juan Martin Del Potro’s dream run at Flushing Meadows with a hard-fought victory against the former US Open champion.
Third seed Wawrinka came from 4-1 down in the opening set to force and win the tie-break but a single break point for the Argentine in the second was enough to level things up but fatigue began to set in on Del Potro, who missed two years of tennis due to a serious injury.
Wawrinka put himself back into the lead before breaking twice in the fourth set to take a 4-0 lead and the crowd sang Del Potro’s name as the Swiss man served for the match to win 7-6 (7/5) 4-6 6-3 6-2 against an emotional Del Potro.
In women’s action, Serena Williams had to dig deep to book her place as the American overcame the gutsy effort of fifth seed Simona Halep to keep hopes pf a record-breaking 23rd grand slam title alive.
Williams dominated with six aces and three break points to take the first set but Halep became the first player to break the American’s serve at this year’s US Open as she fought off 12 break points and converted her fifth set point to pull level.
Halep spurned the chance for a break point early in the deciding set as six-time US Open champion Williams won the next three games to help her secure a 6-2 4-6 6-3 and a place in the final four.
Tenth seed Karolina Pliskova will face the daunting task of denying Williams a place in the final as the Czech reached her first grand slam semi-final with victory over 18-year-old Ana Konjuh.
Pliskova did not face a single break of serve and dropped only five points on her serve as she cruised past Croatia’s Konjuh 6-2 6-2 in just under one hour.
The tenth seed has already defeated one Williams in New York when she sent Venus packing in the last 16 and she will hoping to pull off a major shock to reach the final where either Caroline Wozniacki or Angelique Kerber awaits.