Milos Raonic has hinted that he may sit out the French Open later this month due to a troublesome foot injury.

The Canadian, who also pulled out of the Monte Carlo Masters in April, was clearly struggling when he took to the court against Andy Murray at the Madrid Open on Friday night.

Having already withdrawn from next week's Italian Open, Raonic is now in a race against time to declare himself fit for the second Grand Slam of the season, which gets underway on May 24.

"It is tough when you are not 100% but just squander and squeeze by," the world number six told reporters. "It's something tough to measure, something that can cause extreme amount of pain and is hard to directly treat. Hence, I really got to see where I stand."

Murray continued his pursuit of a second successive clay-court title by beating Raonic 6-4 7-5 in the Spanish capital.