SINGAPORE—During her round-robin match against Maria Sharapova at the WTA Finals, Caroline Wozniacki complained that the lights in the stadium were turning on and off and affected her play. Wozniacki eventually won the match in three sets, but she grew angry during the second set and lost her composure, stopping play to argue with the chair umpire.

The season-ending championship is in its first year in Singapore, where it is featured in a new tennis complex at the Indoor Stadium.

Wozniacki asked the umpire to turn off the lamps. “Well, one time all of a sudden the light show starts going on,” Wozniacki said. “Once there was turned off, then there were two bright lights right in the middle that were all of a sudden turned on; took a couple minutes to turn those off. Then when I went over on the other side they were turned on again. I'm like, 'Really?' They're right in the middle and they weren't on from the start, so that was a little strange.”

Sharapova says that the lights have been worked on for the past week.

“First day I practiced, I think it was Monday last week, it was like dark in the middle of the court and light on the sides, and then the lights went out,” Sharapova said. “That happened for a couple of days. And then they ended up putting enough lights on the center but not enough on the sides.

"I still feel like there is not enough lights on the sides of the court actually. When you're running for a forehand you're actually in a shadow, and then you get back in the court and you're in the light. That's quite different to Istanbul [the location of the WTA Finals during the past three years], but maybe that's just the way it is. Also today some of the stage lights were on; whereas in the last whole week they weren't on. I think that's something Caroline was referring to.”