Sabalenka has had – by her high standards – a strange season.
For the first time since 2022 she has not won a Grand Slam singles title, having lost the Australian Open and US Open finals to Rybakina, and her last title came in Miami in March.
After winning just one of her three matches during the Asian swing, Sabalenka took a break before the season-ending finals.
She faced a tricky task against the crafty Muchova, who was the only player at the event to have a winning head-to-head against her.
The Czech also claimed the first break of the opening set – but, in a pattern that repeated throughout the match, Sabalenka broke straight back.
Muchova served for the first set but a string of errors forced her into a tie-break, and more mistakes gifted Sabalenka the opener.
A topsy-turvy second set featured five breaks of serve, with Sabalenka serving the match out on her second attempt.
Teenager Andreeva, who beat Sabalenka in the 2025 Indian Wells final, was ruthless against Svitolina.
The Russian reeled off seven games in a row against the wayward Svitolina, backed by her impressive backhand.
Andreeva saved all six break points she faced – four of which came in the final game – and hit nine winners to 12 unforced errors in a 77-minute victory.
Elsewhere, Britain’s Cameron Norrie beat Australian James Duckworth 7-5 6-0 to reach the Stockholm Open second round.
Norrie will face top seed Taylor Fritz next as he continues his preparations for this month’s Davis Cup Finals.
Fellow Briton Toby Samuel claimed a 6-3 6-2 win over Leo Borg – son of 11-time Grand Slam singles champion Bjorn – at the same event.