Sabalenka wins WTA Finals opener despite wayward serve

Aryna Sabalenka grappled with her own frustrations and a misfiring serve to begin her WTA Finals campaign with a tight victory over Karolina Muchova.

World number two Sabalenka is bidding to win the season-ending title for the first time in her sixth appearance.

With rival and world number one Elena Rybakina withdrawing on the eve of the competition, Sabalenka is arguably the favourite to triumph on the courts where she won the Indian Wells title in March.

However, neither she nor Wimbledon runner-up Muchova were consistently at their best in the first group two match.

Belarus' Sabalenka battled back from a break down in both sets to win 7-6 (7-2) 7-5.

She cut a frustrated figure at times but reined in her emotions, with her forehand in particular growing stronger as the match progressed.

Her serve, however, was inconsistent. Sabalenka produced seven double faults to four aces, but landed 59% of her first serves and won 33 of 44 points behind it.

"It was a bit tricky with the sun [and] with the shade," Sabalenka told Sky Sports.

"Sometimes I had to adjust my toss, sometimes I had to serve blind, but it's all part of the game."

French Open champion Mirra Andreeva faces Ukraine's Elina Svitolina later on Monday.