Ecstasy and euphoria are the usual emotions World No 1 Serena Williams experiences on a tennis court. On Wednesday, she encountered a different one -- embarrassment.
One of the game's all-time greats, a winner of 18-Grand Slam singles crowns, 63 WTA titles, the owner of four Olympic gold medals, Williams has become accustomed to success.
But on Singapore's purple indoor hard court on Wednesday, Simona Halep took her back 16 years to a time when, as a teenager, she was trying to make a name for herself.
Halep's 6-0, 6-2 success in their Red Group clash at the WTA Finals was the worst defeat Williams had experienced since she was crushed 6-1, 6-1 by Joannette Kruger in the quarter-finals at Oklahoma City in 1998.
Halep served well, pushed her opponent around the court and went for her shots, but Williams, by her own admission, was woeful.
"Yeah, my forehand was off today again. I guess it went on an early vacation," a sombre and downbeat Williams told reporters.
"Lord knows my serve was as well. My serve, I don't even know. My serve was at best in the 10 and under division in juniors.
"Yeah, it was actually embarrassing I think describes the way I played. Yeah, very embarrassing."
Williams had shown no sign of what was to come on Wednesday as she held of the feisty challenge of Ana Ivanovic to start her campaign on Monday with a 6-4, 6-4 victory, her 16th consecutive win in the season-ending championships she has won the last two years.
That was her first action since pulling out of the Wuhan Open because of illness then the China Open with a knee complaint earlier this month.
Characteristically, she didn't blame the knee ailment, which had required extensive rest, for Wednesday's meltdown.
"I'm definitely not 100 percent okay. I'm just here playing, but I'm not nowhere near 100 percent," she said.
"That has nothing to do with today's match. I think Simona played really well and the best match of her career.
"To be quite frankly honest, I'm looking forward to our next meeting because she is making me going to go home and work hard and particularly train for her."
Williams scrambled for a solution during their 65 minutes on court, shrieking at herself, jumping around in between points and going through at least four racquets to find something that worked. All proved fruitless.
She won just nine points as she suffered the ignominy of being bageled in the first set, before finally holding serve in the ninth game to get on the board.
Struggling to get into the match, she simply reverted to clawing another game from the world number four Romanian, who she had beaten in their three previous meetings.
"I'm obviously frustrated and I wanted to do better. I wanted to win more than two games. I was trying for three," she said.
"At one point I was like, If I can just get three games. But that didn't work out for me. But it's okay. You know, things are going and I'm still going to come back and I'm going to be better."
She will be back on court on Thursday night hoping to prove that as she takes on Eugenie Bouchard of Canada with a place in the semi-finals on the line.