Andy Murray reached the second round of the Shenzhen Open after China’s Zhang Zhizhen retired.
Former world number one Murray led 6-3 6-7 (3-7) 4-2 when Zhang, a wildcard at the event in China, ended the match.
The Briton, now ranked 311th as he continues his comeback from hip surgery, saved eight break points as he was given a stern test by the world number 340.
He will face Belgian top seed and world number 11 David Goffin next.
“It’s a really good test for me right now to play against guys who are in and around the top 10,” Murray said.
Murray, a wildcard in Shenzhen, is appearing in his penultimate event of the year after deciding to end his season early.
He has played just 10 matches this year after returning to the ATP Tour in June.
Against Zhang he hit nine aces and won 69% of points on his first serve, but converted just four of a possible nine break points.
Elsewhere, Britain’s Cameron Norrie reached the second round of the doubles event with American partner Denis Kudla, a day after he progressed in the singles draw.
They beat Serbia’s Dusan Lajovic and Viktor Troicki 7-6 (7-5) 6-4 in 76 minutes.