The Belarusian second seed recovered from a break down in both sets to overcome the Czech Wimbledon runner-up in one hour and 57 minutes on the Californian hard courts.

Sabalenka's serve misfired throughout, producing seven double faults against only four aces, though she landed 59 per cent of first serves and won 33 of 44 points behind them.

Muchova, the only player in the draw with a winning head-to-head record against Sabalenka, served for the opening set at 5-4 but a string of errors handed the initiative back to the Belarusian.

Sabalenka dominated the ensuing tie-break 7-2, then navigated a volatile second set that featured five breaks of serve before closing out the match on her second attempt at 6-5.

"It was a bit tricky with the sun and with the shade," Sabalenka said. "Sometimes I had to adjust my toss, sometimes I had to serve blind, but it's all part of the game."

The win marks a positive start for Sabalenka, who is chasing a first WTA Finals title after losing the 2022 and 2025 finals, and arrives after a season in which she reached the Australian Open and US Open finals but lost both to world number one Elena Rybakina.

Rybakina withdrew on the eve of the tournament with a viral illness, leaving Sabalenka as the highest-ranked player in the field and the favourite for the season-ending crown.

Sabalenka's last title came in Miami in March, and she won only one match during the Asian swing before taking a break to prepare for the finals.

In the other Group Two match later on Monday, French Open champion Mirra Andreeva faced Ukraine's Elina Svitolina.

On Sunday, Coco Gauff outlasted fellow American Jessica Pegula 6-4, 6-7 (5-7), 6-2 in a two-hour 39-minute Group One opener, improving her career record against Pegula to 6-5.

Reigning Wimbledon champion Linda Noskova completed the Group One opening round with a 6-2, 6-4 win over Marta Kostyuk.

This year's WTA Finals were originally scheduled for Saudi Arabia but were relocated to Indian Wells in July following US military strikes on Iran in February and the subsequent regional conflict.

The eight-woman field continues round-robin play through the week, with the top two from each group advancing to the semi-finals on Saturday.

Brief scores: Sabalenka bt Muchova 7-6 (7-2), 7-5.