By Daniel Chavkin The 25-year-old had to retire in his match vs. Rafael Nadal due to an ankle injury. View the original article to see embedded media. Alexander Zverev’s French Open run ended early on Friday when an ankle injury forced him to retire from his semifinal match vs. Rafael Nadal. Zverev was down a set and in the middle of a competitive second set when he suffered the injury, and he needed crutches to leave the court. After the match, Zverev posted an update on his Instagram story, saying that the injury seems like it is going to be a problem. “Looks like I have a very serious injur…