Caroline Wozniacki shouldered all the blame for her shock loss to world number 149 Petra Cetkovska at the US Open on Thursday night.
The Dane would squander no less than four match points on her way to a 6-4, 5-7, 7-6(1) defeat on the hard courts of Flushing Meadows.
"I can only blame myself," the 25-year-old told tennis.com.
"You always think back: I should have done this, I should have done that. I let her play well."
The former world number one has had a poor year so far by her standards, winning just one title in Kuala Lumpur in March.
As for the grand slams, Wozniacki reached the fourth round at Wimbledon but crashed out in just the second round of the Australian Open, French Open and now the US Open.
"I'm obviously not thrilled with the grand slam year, that's for sure," added the current world number five.
"I think I can do much better."
Meanwhile, Cetkovska was over the moon to record the win, her first over a top ten player. The Czech also thanked the crowd in the Arthur Ashe Stadium for creating a great atmosphere.
"I was so happy to be able to be back and to compete…and this happens tonight, in front of all of you," said the 30-year-old.
"It's amazing for me. The atmosphere, it's nowhere else. We want to play in front of you guys every day… we never can get enough! So it was just keeping me alive and I wanted to fight until the end."