LOS ANGELES (AFP) - South Korea's Ryu So Yeon won the ANA Inspiration with a birdie at the first play-off hole on Sunday, beating Lexi Thompson after the American was left in tears by a rules fiasco that cost her four strokes.
Thompson was in the lead of the year's first women's Major when she learned after the 12th hole that she was being penalized for an infraction the previous day, spotted by a television viewer.
She nevertheless birdied three of the last six holes to force the playoff, but could not match Ryu's play-off birdie on the 18th hole.
The penalty imposed on Thompson, 22, occurred after a television viewer alerted the LPGA that the American golfer had marked her ball then replaced it in the wrong place on the 17th hole a day earlier.
Thompson reacted with disbelief when officials told her of the decision while she walked to the 13th tee.
"Is this a joke?" Thompson asked.
After being assured it was not, she responded: "This is ridiculous."
The LPGA later said in a statement: "On Sunday afternoon, the LPGA received an email from a television viewer that Lexi Thompson did not properly replace her ball prior to putting out on the 17th hole during Saturday's third round of the ANA Inspiration."
It added that after a full review it informed the player of the four-stroke penalty as she walked to the 13th hole. Thompson gathered her composure and had an eagle putt to win on the last hole, but settled for birdie to force the play-off against Ryu.
Her playing partner, Suzann Pettersen, said: "I thought it was serious when two rules officials came out. "For her to come back with those birdies shows the character she is. I have got goose bumps."
Tiger Woods immediately came to Thompson's defense on Twitter.
"Viewers at home should not be officials wearing stripes," Woods wrote. "Let's go @Lexi, win this thing anyway."
Speaking after the play-off, an emotional Thompson said: "[The fans] got me through the whole round.
"I felt strong through the finish and it felt great to see the fans behind me.
"I wasn't expecting what happened today, but it is what it is and I'll learn from it. I fought strong and that's all I could do."