"It is with deep regret that I have to withdraw from tomorrow's Boston Marathon", Hasay wrote.
When we spoke to Hasay on Friday, she said her foot was "doing great" and that she had not missed a workout since withdrawing from the World Half Marathon Championships on March 24 with a tight plantar.
Last year, Hasay set the record for the fastest debut ever for an American woman in the Boston Marathon by three minutes, finishing third with a time of 2:23:00.
A wreath was laid at the finish line of the Boston Marathon this Sunday morning to mark the anniversary of the deadly bombing five years ago. Hasay, who is part of the Nike Oregon Project, finished in third place previous year.
The world's best distance runners are gearing up for one of the most anticipated events in their sport: The Boston Marathon.
She had been running pain-free in recent weeks but an MRI scan revealed a stress reaction.
"Her doctor and team have made the decision that Jordan needs to take time to recover fully so there is no long-term injury", the statement said, adding that officials support Hasay's decision and invite her to return to Boston in 2019.
The 26-year-old's build-up to the Beantown race was not ideal as she withdrew from the IAAF World Half Marathon Championships with a sore foot, though she told us at the press conference that her foot was "doing great" and feeling "100 percent".
American runner Jordan Hasay, who finished third among women at last year's Boston Marathon and was seen as a contender this year, announced on Twitter that she has withdrawn from tomorrow's race because of a foot injury.