An injury to Julien Benneteau allowed Andy Murray to progress to the quarter-finals of the Monte Carlo Masters.
The Frenchman hurt his ankle after falling while sliding on the clay with the match finely poised at 5-5 in the first set.
Benneteau was immediately treated by on-site medical staff with Murray helping to fetch ice to calm the swelling.
The 30-year-old tried to play on with Murray going 6-5 ahead but he was unable to continue, retiring at the end of the game.
The withdrawal of the world number 31 maintains Murray’s short time on court during the tournament so far.
The world number four took just over an hour to beat Serbian Viktor Troicki on Tuesday.
He will now face Tomas Berdych in the next round after the number six seed beat Japan's Kei Nishikori 2-6, 6-2, 6-4.