Kim Clijsters moved into the US Open women's singles final in controversial circumstances as defending champion Serena Williams picked up a point penalty for a second code violation on match point against her.
Clijsters had been a set and 6-5 up when Williams was foot-faulted on a second serve to hand the Belgian wild card and 2005 champion match point.
Replays indicated the call had been a harsh one and it certainly incensed the American second seed, who quickly moved towards the linesperson, pointing, ball in hand while she unleashed a verbal tirade and then waved her racquet angrily at the woman, who was then beckoned by chair umpire Louise Engzell to explain what had been said.
Williams had picked up a first code violation for smashing her racquet at the end of the first set and this time tournament referee Brian Earley was called to the chair.
After discussing the situation with the player, linesperson and chair umpire, Williams was handed a second code violation, the resultant point penalty handing victory to a bemused Clijsters, 6-4 7-5.
No announcement was made from the chair and the first Clijsters learned of the result was when Williams walked over to her side of the court to shake her hand.
"It was not a default, it was a point penalty that happened to be given on match point," Earley explained.
"There was an earlier warning for racquet abuse and she was called for a foot fault and she said something to a line umpire and it was reported to the chair and that resulted in a point penalty.
"It was a code violation for unsportsmanlike conduct."
Williams, facing the press 10 minutes after the match, appeared calm but said she could not recall what she had said to the linesperson.
"I said something that I guess they gave me a point penalty. Unfortunately it was on match point," Williams said.
"I didn't threaten...I don't remember anymore to be honest. I was in the moment and everyone's fighting for every point."
As for the call that sparked the Williams tirade, the outgoing champion said: "I've never been foot faulted (all year) and then suddenly in this tournament they keep calling foot faults.
"I'm not going to sit here and make an excuse. If I foot faulted, I did. It is what it is and that's basically all it was."
Williams, though, said she did not regret losing her temper.
"I haven't really thought about it to have any regrets. I try not to live my life saying: 'I wish, I wish' but I was out there and I fought and I tried and I did my best."
Clijsters was still confused by the events that handed her the match-winning point.
"I was just trying to be focused ahead of match point. I started to get ready to return (when) I saw Serena talking to the linesman over there, but I was too far away to hear what was going on, so I can't really comment on anything that happened out there."
The Belgian, playing just her third tournament since coming out of a 27-month retirement during which time she became a mother for the first time, will now face ninth seeded Caroline Wozniacki of Denmark in Sunday night's final.
"I came out of the blocks really well, hitting the ball and seeing it really well. I kept her on the back foot.
"She had a few games where she was serving really well, up to 120 miles per hour and I just tried to stay in those games.
"I'm still in shock."
Clijsters deserves her place, having outplayed Williams, whose usually dominant serve deserted the American for much of the match.
Williams also saw her second serve exploited, her unforced error count hit 31 and had been unable to build on her breaks of serve by allowing Clijsters to break back immediately twice in the second set.
Williams had gone into the match having won seven of their eight previous meetings, although the most recent encounter had been in 2003.
It was Williams who had looked most tense as the match got underway, 85 minutes after its scheduled start and more than 24 hours later than the intended match time due to heavy rain.
Williams looked tentative and did not seem to be moving as freely as in previous rounds. The sixth game saw Clijsters go a break up at 4-2. The champion broke straight back but then was broken again as Clijsters took the opening set.
Having netted a forehand, her 14th and final unforced error of the set, the champion demolished her racquet with a huge, frustrated smash into the ground that earned her the first code violation.
Williams served to stay in the match at 6-5 down and despite going ahead early in the game, Clijsters fought back before the fateful foot fault intervened.