Murray marks 37th birthday with opening win in Bordeaux Challenger
The three-time Grand Slam champion and former world number one was 7-5, 2-0 ahead of Kyrian Jacquet when the French player retired injured.
Jacquet, ranked a lowly 219 in the world and a qualifier at the clay-court event, was suffering with what appeared to be a right leg problem.
Murray, ranked 77, who has already announced he is "unlikely to play beyond the summer" was taking part in his first match since injuring his ankle in Miami.
He will face another home player Gregoire Barrere for a place in the quarter-finals of a tournament being used as a warm-up for the French Open which gets underway on May 26.
Murray also played at Bordeaux in 2023 where he was defeated by fellow three-time major winner Stan Wawrinka in the first round.