Over the past 10 years, Mutai has completed 20 marathons. Even among the top competitors at a race like Boston, he is exceptionally experienced, with nine podium finishes--two victories and second place seven times. His career best of 2:03:13, achieved at the 2014 Berlin Marathon, is the fourth-fastest mark, just 16 seconds shy of the world record. Mutai entered Boston with the fastest time of all competitors. The deep field featured two Olympic medalists in the distance and four other men who have run sub-2:05, the current benchmark for the world’s best, including Kenyan Wilson Chebet and Ethiopians Lemi Berhanu Hayle and Yemane Tsegay.

But when it comes to marathons, every race is a blank slate. Former champions are vulnerable to being defeated by guys of equal caliber that train as hard and surrender just about everything. “You have to sacrifice yourself. It’s necessary,” says Daniel Salel, Mutai’s training partner of eight years, who also came to Boston to race.

Mutai’s prerogative to seal a winning fate in Boston began at dawn last November at Chirchir-Center, one of the top training camps near Kaptagat, a village in the Kenyan highlands, where he ran more than 100 miles a week. Desire was an alarm clock that woke him before 6 a.m. six days a week. After a simple breakfast of tea and bread with honey, Mutai would begin the first of two demanding training sessions.

For 12 to 13-miles, he would run alongside 30 or so fellow professional Kenyan runners, all working toward a similar goal: to become a champion. Again in the afternoon, Mutai ran about 6 miles, between resting, massage and small meals. It’s a monkish lifestyle he’s lived since turning professional in 2004, one that shuts out distractions. During training, Mutai must live an hour from his wife and three children for all but one day a week.

Mutai hails from the Nandi tribe, a subtribe of the Kalenjin, an ethnic group in Kenya that has produced many of the world’s top distance runners, including marathon world record holder Dennis Kimetto. “I think we’re the best athletes in the world,” he said without pause after his shakeout run the morning before the race in reference to Kenyan runners. He’s of no relation to countryman Geoffrey Mutai, who set the Boston Marathon course record in 2011. One of six siblings, Mutai grew up running 10 kilometers a day to get to and from school. At age 15, “I realized that I had a talent,” he said. He’d often win competitions organized by his school.

He pursued the sport professionally after graduating from high school and joined an elite camp to train full time. “I was not expecting to reach this level. But because of my commitment, it made me at this level.”

“This is my career, so I want to make sure at the end of it I will have achieved what I could. I’m still trying my best to see if I can run good times,” he says. “You try as much as you can until you’re not able.”

In Boston, Mutai tried his best. Before his race started to collapse at mile 18, he was on pace to contend for the win. The point-to-point Boston course stretches 26.2 miles from Main Street in the rural New England town of Hopkinton, Massachusetts, to several suburban neighborhoods and finishes on Boylston Street in downtown Boston. Mutai led from the beginning through Hopkinton to Ashland and into Framingham before reaching Natick. He still led mid-way through the race when he approached Wellesley College. Everything was going according to plan.

The temperature peaked at 79 degrees by the halfway mark. Not long after, Mutai’s body stopped absorbing the fluids stationed every five kilometers along the course. He had prepared eight of them the evening prior in his hotel room, meticulously mixing a powdered raspberry-flavored sports drink with water, tasting each batch before sealing the lid and wrapping the bottles in hot pink tape.

“Everyone can maintain the pace until 30K, and from there, you can decide to make a move. That is the time that will determine how strong you are,” Mutai said three days before the race. “You go for a win. You cannot say you’re going for the fastest time. It doesn’t matter. The most important thing is winning.”