So Yeon Ryu defeated Lexi Thompson with a birdie on the first play-off hole to win the ANA Inspiration in Rancho Mirage, California, as the first Major of the year ended in controversy.

During Sunday’s final round, 2014 ANA Inspiration champion Lexi Thompson was alerted in between the 12th and 13th hole that she had been assessed a four-stroke penalty for a rules infraction. That penalty dropped her from a two-stroke lead to a two-stroke deficit. She was able to regroup, refocus and resume her game, ultimately making a birdie on the final hole to force a play-off with Ryu.

On Sunday afternoon, the LPGA received an e-mail from a television viewer, saying 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. The claim was quickly investigated by LPGA Rules officials.

After a full review, it was determined that Thompson breached Rule 20-7c (Playing From Wrong Place), and received a two-stroke penalty under Rule 16-1b. She incurred an additional two-stroke penalty under Rule 6-6d for returning an incorrect scorecard in round three. She was immediately notified of the breach by LPGA Rules Committee in between holes 12 and 13 of the final round.

“I learned a lot about myself and how much fight I do have in me,” said Thompson. “And I don’t know, every day is a learning process, and I wasn’t expecting what happened today but it is what it is. It happens, and I’ll learn from it and hopefully I’ll do better.”

The victory is the fourth career win for Ryu and her second major victory, as she also captured the 2011 U.S. Women’s Open.

“I just, you know, cannot believe this situation. During play, I didn’t even check the leader board, but I thought Lexi played really, really well,” Ryu said after her round. “I thought, I’m well behind, so all I wanted to do was just play my game and enjoy my game. I was paired with my best friend, Inbee Park today, so I just really wanted to have a really good, strong finish.”

There was a strong showing from the European Solheim Cup prospects, who will receive points for their top-20 finishes in a Major. Suzann Pettersen tied for third place alongside Olympic gold medallist Inbee Park and Minjee Lee. Karine Icher was 10th, Anna Nordqvist tied for 11th and Charley Hull tied for 14th place.

The next women’s Major is the KPMG Women’s PGA Championship on June 26-July 2, followed by the US Women’s Open conducted by the USGA on July 10-16, then the Ricoh Women’s British Open on July 31-August 6 and then the Evian Championship on September 11-17.