BOSTON (CBS) – A calf injury has forced American runner Meb Keflezighi to pull out of the 117th running of the Boston Marathon.

Keflezighi has run Boston twice, finishing third in 2006 and fifth in 2010.

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One of America’s most accomplished runners, Keflezighi won the silver medal at the 2004 Olympic Marathon, won the 2009 New York City Marathon, and recently finished fourth at the 2012 London Olympic Marathon.

Keflezighi said Friday he hopes to return to race in Boston next year.

“Despite my best efforts, a nagging injury to my calf has not healed sufficiently, so I have to withdraw from the Boston Marathon,” Keflezighi said in a release from John Hancock, the races primary sponsor.

“I’m very disappointed. My training was going well in January and February, which had me very excited about the possibilities this spring.”

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“I even skipped the NYC Half Marathon to focus on getting healthy for Boston, but unfortunately, it wasn’t enough. I ran out of time to recover enough to compete for a victory at the Boston Marathon. Nevertheless, I will still be coming to Boston to attend events for John Hancock and look forward to supporting the most prestigious marathon in the world.”

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Kenyan Laban Korir has also dropped from the race due to a recently developed groin injury. Korir, who has a 2:06:05 personal best, said he made the difficult decision to withdraw.

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Tune in to the 117th Boston Marathon on April 15, 2013 on WBZ-TV, the only station with start-to-finish coverage of the race!