By Toby Davis
LONDON, June 26 (Reuters) - Wimbledon marathon man John Isner was forced to retire after two games of his second round match against Frenchman Adrian Mannarino with a knee injury on Wednesday.
American Isner, who wrote his name into Wimbledon folklore when he played in the longest match in professional tennis in 2010 against Nicolas Mahut, pulled up while serving at 1-1 in the first set.
The 18th seed received extensive treatment on Court Three, including having his left knee strapped up, and attempted to battle through the pain barrier but could not continue.
After throwing in the towel, he told reporters: "I didn't feel anything in my first match; didn't feel anything yesterday in practice; didn't feel anything today in (the earlier) warm-up; didn't feel anything in the five-minute warm-up; didn't feel anything in the first two points of the match; and then, bam, felt it."
Isner is famous for his part in a record 11-hour-five-minute first round match at Wimbledon against Frenchman Mahut which he won 70-68 in the fifth set.
He came through his first round this year against Russia's Evgeny Donskoy in straight sets.
Isner said he was due to have a scan later on Wednesday before flying back home.
"I'm coming back later to get a more definitive answer of what exactly is going on," he added.
"I want to get the hell home, go back to the States, and get ready from there." (Reporting by Toby Davis; editing by Ken Ferris)