Fręch, ranked No. 53 in the world, took the opening set 7-6 and was leading 4-1 in the second when the 22nd-ranked Muchová pulled out due to exhaustion in hot conditions, Poland’s state news agency PAP reported.
The 27-year-old Pole opened her women’s singles campaign with a 6-3, 2-6, 6-3 win over Russia’s Veronika Kudermetova.
She will next face Germany’s Laura Siegemund.
Meanwhile, Poland's world No. 2 Iga Świątek cruised past Marie Bouzková of the Czech Republic 6-1, 6-1 to set up a third-round clash with Switzerland’s Belinda Bencic.
Fellow Pole Magda Linette exited in the first round after a 2-6, 3-6 loss to Croatia’s Antonia Ruzic.
The Wuhan Open runs until Sunday.
(gs)
Source: IAR, PAP