Russian tennis player Olga Puchkova was defaulted from her match at Citi Open after hitting a line judge in the knee with a ball after losing a point in the third set.

Puchkova, ranked No.88, forfeited her match against Paula Ormaechea of Argentina while trailing 3-6, 6-3, 4-1 Thursday during their second-round match.

Puchkova said it was an accident and that she was "sincerely sorry," following the injury.

"I wasn't looking where the tennis ball would go," Puchkova said according to reports.

Puchkova later stated that she had apologized to the line judge after the incident.

According to tournament rules, Puchkova had to be removed, and Women's Tennis Association supervisor Melanie Tabb told the Associated Press that even though she believed Puchkova did it un-intentionally, she was obligated by tournament rules to kick her out.

"I 100 percent believe her that that's true - that she didn't mean to do it," Tabb said to the Associated Press. "She wasn't even looking in that direction. She was just hitting the ball in frustration after she lost a point,"

After the line judge was hit with the ball, match chair umpire Carrie Hinueber cited her for code violation and consulted with Tabb for the ruling.

"She didn't mean to do it, but it happened," Tabb said. "Clearly, you hit someone with a ball, that's pretty much a default situation."

Citi Open is a tournament designed to be a tune-up for the US Open, and Puchkova defeated second-seeded Sloane Stephens in an upset Monday in first-round action before being disqualified Thursday.