Venus Williams won her 47th WTA singles title as opponent Garbine Muguruza pulled out of the Wuhan Open final with an ankle injury when trailing 6-3 3-0.
Both players came into the tournament less than fully fit, with Williams, 35, struggling with a thigh problem.
The American, a seven-time Grand Slam champion, used her experience to good effect in the first set of the final.
She broke Wimbledon finalist Muguruza twice in the second set before the 21-year-old Spaniard withdrew.
"I'm very sorry to have had to retire, but sometimes the body just doesn't recover," said Muguruza.