"I'm sorry guys," China's Zheng Jie told the Flushing Meadows crowd after stunning home favourite Venus Williams - and perhaps ending the two-time champion's US Open career.
Zheng dumped out the seven-time grand slam winner 6-3, 2-6, 7-6 (7-5) after an epic match lasting just over three hours, tied for the fifth-longest women's match since 1970 at the tournament.
At 33, and slowed down in the past couple of years by an auto-immune disease that saps energy, and hampered much of this season by a bad back, Williams was asked what the future holds for her at the US Open.
In one breath, Williams brushed aside the unspoken reference to retirement, saying: "I definitely want to come back for the atmosphere." And in the next, she added: "I mean, next year's Open is so far away right now."
Defeat to the 56th-ranked Zheng was the third year in a row that Williams is out after two rounds. "If I didn't think I had anything in the tank, I wouldn't be here," said Williams, who was ranked No 1 in 2002 and is currently 60th. "I feel like I do, and that's why I'm here."
The American acquitted herself well for stretches, erasing deficits over and over again, until she simply ran out of solutions against Zheng.
"I just kept trying to fight today," Williams said.
The third set alone lasted 1½ hours. "I was like, 'Wow, this is a marathon'," Williams said.
Near the finish line, she faltered. On the final two points, Williams missed a volley, then a return. She wound up with 44 unforced errors in all, half on forehands, in part because Zheng kept scrambling along the baseline to get to balls and block them back, making Williams hit extra shots.
During her on-court interview, Zheng addressed the partisan crowd that was raucously pulling for Williams in Louis Armstrong Stadium, apologising then adding: "She is a very good player but I wanted to win also."
Every point Williams won, it seemed, drew clapping and screaming from on-their-feet spectators. "I love that. I wish I could play some more for that," Williams said. "I want to come back here just for that, at this point."
Zheng led 4-1 in the tiebreaker, before Williams made one last stand. But at 5-5, Williams put a backhand volley into the net as she lost her footing. "I should have made the shot," Williams said. "I was just rushing."
That gave Zheng her first match point, and Williams' backhand return missed, ending her stay in the singles draw as Zheng jumped for joy in triumph.
"Today is a tough match for me. Unbelievable I can beat her," Zheng said.
"The second set I lost my concentration and she played so great. The final set we were fighting each other. I think this is very good for me and will help me for the next match."
Zheng now plays Spanish 18th seed Carla Suarez Navarro.
Williams hasn't been ranked in the top 10 in 2½ years. The last time she made it beyond the third round at a major tournament was a fourth-round appearance at Wimbledon in 2011.
At the 2011 US Open, Williams withdrew before her second-round match, announcing she had Sjogren's syndrome, an illness that causes joint pain and fatigue.
"I feel like it's definitely affected my game, but I'm working on it," she added. "I'm a fighter."