Aug. 26 (UPI) -- Twenty-three time Grand Slam winner Serena Williams cited complacency and fatigue after she took a three-set upset loss to Maria Sakkari in the round of 16 at the Western & Southern Open.
"I literally put myself in this situation," Williams told reporters after the 5-7, 7-6 (5), 6-1 setback Tuesday at the USTA Billie Jean King National Tennis Center in New York City.
"You know, it's like dating a guy that you know sucks," Williams added. "That's literally what I keep doing out here. It's like I have got to get rid of this guy. It just makes no sense. It's frustrating."
Williams had 58 errors while Sakkari had 43 miscues in the two-hour and 17-minute clash. Sakkari edged Williams 27 to 25 in winners and had seven aces.
"It was tough," Williams said. "I literally should have won that match. There was no excuse. It was hard, but I had so many opportunities to win, and I have to figure that one out ... how to start winning those matches again.
"I started cramping, but I shouldn't have been in that situation. I don't think that helps mentally when it's like, you know the match is over and you have won the match, and now your legs were already tired and now they are even more tired, and now it's even more tired."
Williams -- ranked No. 9 in the world -- appeared in control after she took a 5-2 lead in the first set. Sakkari then rallied to tie the set at 5-5 before Williams won the final two games.
Sakkari -- ranked No. 21 -- jumped ahead 3-1 in the second set before Williams won the next four games. Williams then served for the match before Sakkari rallied to win the second set. Sakkari went ahead 5-0 in the final set before Williams saved seven match points to stay in the contest.
Sakkari finally claimed match point with a forehand winner to end the affair.
"I haven't realized it yet," Sakkari said of the win over Williams. "It feels pretty good because she has been a role model for me growing up, and obviously what she has achieved is huge. So it feels very nice."
Sakkari, 25, beat Cori "Coco" Gauff in the first round before a victory over Yulia Putintseva in the second round. Williams beat Arantxa Rus to advance to her match against Sakkari.
Sakkari will face No. 8 seed Johanna Konta in the quarterfinals at 5 p.m. EDT Wednesday in New York.