In Hasay's own statement, she expressed regret for withdrawing. According to the race management, Hasay had an MRI today that revealed the injury.
Thousands of people took part or lined the street to cheer on their family and friends who were taking on the Boston Marathon, Half Marathon and Fun Run events.
Hasay, New York City Marathon victor Shalane Flanagan and fellow Americans Desiree Linden and Molly Huddle had been expected to challenge Kenyan defending champion Edna Kiplagat to end the nation's 33-year wait for a home victor in the women's race.
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. It's her first time running in the race.
Hasay, an Arroyo Grande native and Mission Prep graduate, had been running pain-free in recent weeks and recovered from plantar fasciitis. Her doctor and support team decided it would be better for her to fully recover before racing again.
Manchester City clinch Premier League title
Manchester United hold the current record of Premier League winning margin of 18 points and City and breach this feat too. I'd like to stay humble - this is not a dynasty, it's one title. "West Brom is a club I care about a lot", he said.
"It was the right decision", Hasay told The Tribune in a phone interview from Boston on Friday.
Boyarko said she is feeling good and up for the race but the weather could be challenging.
The 26-year-old's build-up to the Beantown race was not flawless 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".
Hasay was considered one of the top contenders.