Shaken by his shocking US Open quarter-final loss to Tomas Berdych, World No. 1 Roger Federer is going "back to the drawing board" to try and pick up the pieces of a suddenly shattered season.
Czech sixth seed Berdych stunned the Swiss top seed 7-6 (7/1), 6-4, 3-6, 6-3 on Wednesday to book a berth in Saturday's US Open semi-finals against British third seed Andy Murray, who beat Croatian Marin Cilic 3-6, 7-6 (7/4), 6-2, 6-0.
"I've got to go back to the drawing board from here and see what's priority," said Federer. "I'm disappointed. I really expected myself to play better."
Federer saw his 21-match unbeaten run in night matches at Arthur Ashe Stadium snapped by a rival whom he had beaten in 11 of 15 prior meetings, one who had never played a night match in the largest Grand Slam tennis venue.
After collecting his first Grand Slam title in 2 1/2 years by beating Murray in the Wimbledon final, taking an Olympic silver medal and reclaiming the World No. 1 ranking, Federer was handed his worst US Open loss since a fourth-round ouster in 2003 by David Nalbandian.
"The goal has been achieved, but now this is disappointing for me," Federer said. "We'll see where I go from now and if I go to Davis Cup or not, about what's to come for the remainder for the season."
Fighting for the season-ending World No. 1 spot will play a role in his decision once the sting of defeat has eased.
"No. 1 has another role to play," Federer said. "But this is obviously a setback."
Federer was trying to become the first man in 87 years to win a sixth US Open and capture his 18th career Grand Slam title. Instead, he missed out on what would have been a 33rd Slam semi-final and ninth in a row in New York.
"I always know I'm going to put in the best fight. I did that," Federer said. "I wish I could have played better. So many moments I thought, 'Man, it's just not happening for me.' It was just a very disappointing match.
"I just didn't come up with the goods tonight. It was unfortunate."
Federer had not played since Saturday as a result of advancing by walkover on Monday when American Mardy Fish withdrew over health issues, but the legend dismissed any notion that the layoff had anything to do with his failure.
"I don't think the schedule was a problem," Federer said. "I should come in here with tons of energy and ready to go.
"If you get that match in with Fish, come through with more confidence, maybe the first three matches didn't quite give me that, who knows? I don't put that down as a negative, really."
Berdych made only 21 unforced errors in the match to 40 by Federer, who smacked 44 winners to 30 for Berdych but won only 45 percent of second-serve points to 51 percent for Berdych.
"I rarely go through matches where I have no chances," Federer said. "I missed some but that's normal. He probably created more than I did and that's why he ended up winning.
"I felt good. Such an amazing summer I had. I really thought I was going to come out and play a solid match. I didn't do that. Obviously there's a bit of a letdown now."