New York ? Any time now, Andy Murray will break through and become Britain’s next Grand Slam champion.

Or so the theory goes.

The fourth-seeded Murray, expected by many to make a deep run at this year’s U.S. Open, instead made his second straight earlier-than-expected exit from Flushing Meadows — losing to No. 25 Stanislas Wawrinka on Sunday in the third round.

Wawrinka rallied from a break down late in the second set for a 6-7 (3), 7-6 (4), 6-3, 6-3 upset — a loss certain to be picked apart by the tennis-loving fans back home.

“I have no idea of whether I’ll win a Grand Slam or not,” Murray said. “I want to. But if I never win one, then what? If I give 100 percent, try my best, physically work as hard as I can, practice as much as I can, then that’s all I can do.”

Murray is trying to become the first British man to win a Grand Slam tournament since 1936. He was a popular pick this year, based on trips to the finals at Flushing Meadows two years ago and this year’s Australian Open, along with a championship in Montreal last month in which he beat both Rafael Nadal and Roger Federer.

Instead, the loss to Wawrinka goes with a fourth-round exit last year.

The promise of a deep run this year for Murray slipped away quickly after the second set. The 23-year-old Scot needed the trainer twice after that — once for tightness in his quad, another when he felt tingling in his right elbow.

On the women’s side, Venus Williams, who struggled with her serve and kept yanking at the hemline of her red, sequin-dotted dress, eventually solved 16th-seeded Shahar Peer 7-6 (3), 6-3 to reach the quarterfinals in New York for the 10th time.