Svetlana Kuznetsova hacked off part of her own hair at a changeover as she beat Agnieszka Radwanska 7-5 1-6 7-5 at the WTA Finals in Singapore.
The Russian, 31, who qualified for the event ahead of Britain's Johanna Konta, cut her thick plait in half with scissors at the start of the third set.
"It was bothering me a lot. When I was hitting the forehands I hit a good shot and it would hit my eye," she said.
"I thought, 'what's more important? My hair, which can grow, or the match?'"
Kuznetsova asked the umpire to supply her with a pair of scissors to carry out her impromptu haircut.
Defending champion Radwanska said she was unaware of the incident, but agreed with her opponent's priorities.
"I didn't even know that," said the Pole. "Good thing she didn't cut her anything else. I think hair is not very important."
It was just one dramatic moment in a three-hour match in which Kuznetsova recovered from 4-1 down to take the first set, saved a match point in the third and was tearful at a changeover before prevailing.
Kuznetsova endured a hectic build-up to the season finale, winning the Kremlin Cup in Moscow on Saturday to collect the ranking points she needed to edge out Konta in the race for the eighth and final qualifying spot before flying to Singapore.
It is not the first time a tennis player has taken action after being distracted by their own locks on court. Britain's Andy Murray snipped his fringe during his defeat by Rafael Nadal at last season's ATP Finals.
In the White Group's other match in Singapore, Karolina Pliskova also saved a match point as she overcame French Open champion Garbine Muguruza 6-2 6-7 (4-7) 7-5.
World number one Angelique Kerber, who beat Dominika Cibulkova in her Red Group opener on Monday, takes on Simona Halep in the pick of Tuesday's matches, with Cibulkova playing Madison Keys in the other match.
Two players will progress from both the Red and White Groups to contest the semi-finals.