One of Canada's best distance runners hit "the wall" at mile 22 on Sunday.
The world-record holder in the marathon recently Tweeted he needs more time to think things over.
Japan's top marathoner pulled out because of "intense abdominal pain".
This year's ING New York City Marathon runner-up will now return to the track.
Sammy Wanjiru had hoped to race his top rival.
The New York Road Runners CEO was shocked when she heard of the great marathoner's retirement.
Despite top-10 finish, he 27-year-old wasn't pleased with his performance on Sunday.
Cameras followed Edison Pena every step of the way.
The 34-year-old older sister of deceased U.S. runner Ryan Shay missed starting the ING New York City Marathon due to an emergency
The marathon world-record holder makes shocking announcement after dropping out of the ING NYC Marathon.