Serena Williams pulled out of her French Open fourth round encounter against Maria Sharapova due to an arm injury on Monday. The 36-year-old said she had suffered a pectoral muscle injury in her third-round win over Julia Goerges and “can’t serve at all”.“Unfortunately I’m having some issues with my pec muscle. Right now I can’t actually serve it’s kind of hard to play,” she told the reporters.ALSO READ: Simona Halep routs Elise Mertens to reach French Open last eight“I’m having an MRI (scan) tomorrow, I’m going to stay here to see the doctors and see as many specialists as I can. I won’t know (how serious the injury is) until I get those results.”Williams had worked hard to get back in shape and was making her Grand Slam comeback at the French Open following the birth of her daughter Alexis Olympia last September.“Physically I’m doing great. It hasn’t been easy. I sacrificed so much to be at this event. I’m going to continue to get better. I had such a wonderful performance in my first Grand Slam back,” she added.She was unable to say whether or not she would be fit for Wimbledon which gets underway in four weeks’ time.Serena Williams defeated Goerges 6-3, 6-4 in the third round to set up a clash against Sharapova who made short work of Czech sixth seed Karolina Pliskova 6-2, 6-1.ALSO READ: Caroline Wozniacki stunned by Daria Kasatkina, crashes out of French OpenWilliams, the champion in 2002, 2013 and 2015 and playing her first Slam since giving birth to her daughter in September, last took part a major at the Australian Open in 2017.Sharapova and Williams have met 21 times, with the American leading the head-to-head record 19-2 after 18 consecutive wins. Sharapova has not defeated her fellow former world number one since 2004 -- a streak of 18 matches – the same year when he burst into the world tennis scene.It will the first time the two were going to face each other since the American’s win in the 2016 Australian Open quarter-finals -- Sharapova’s last match before serving a 15-month doping ban.“Any time you play against Serena you know what you’re up against. You know the challenge that is upon you. You know, despite the record that I have against her, I always look forward to coming out on the court and competing against the best player,” said the 31-year-old Sharapova, after her third-round victory.