30-year-old American is in the midst of a comeback, and he hopes his hard work pays off in Boston.
Four-time U.S. Olympian is the fourth elite runner to withdraw from the race.
The four-time Olympian is confident heading into his 13.1-mile debut.
Five U.S. Olympians will take part. Event to be broadcast live locally on WABC-TV and nationally on ESPN3.
Forty eight athletes from 14 countries will take part.
The race will include five of the six marathoners from the 2012 U.S. Olympic team.
He will still be giving the New York City Marathon a shot.
Event record holder Abdi Abdirahman and Kara Goucher will compete.
Meb Keflezighi talks about his mindset heading into Sunday's Olympic Marathon,
Will we see another surprise on the streets of London?