This former BYU star will miss the Boston Marathon — but other former Cougars will run

Clayton Young, left, and Conner Mantz, practice at the BYU track in Provo on Thursday, April 10, 2025. | Laura Seitz, Deseret News

Conner Mantz, the Olympic marathoner from BYU and Smithfield, Utah, has managed an uninterrupted streak of eight marathons that stretches back to 2022 in which he produced seven top-seven finishes and an American record.

This is almost unheard of in a sport so fraught with injuries and setbacks resulting from 125-mile training weeks and the perilous 26.2-mile race itself, but that streak is finally coming to an end.

Mantz was scheduled to race in Monday’s Boston Marathon but withdrew three weeks ago due to an injury — a sacral stress fracture.

“It’s tough when you’re the American record-holder and (the Boston Marathon) is wanting you and incentivizing you to run,” says Mantz’s long-time coach, Ed Eyestone. “It’s tempting even when training isn’t perfect, but we made the right call (to withdraw).

“We didn’t want to go there at 80 percent. We need to protect the Mantz brand. We need to respect the event and the marathon and the distance and the competition. This is not the local fun run.”

After claiming two individual NCAA cross country championships, Mantz left BYU in 2021 and undertook professional road racing and marathoning. With the exception of the 2023 Boston race, he has been the top American finisher in seven of those eight races and ran 2:09:00 or faster each time. He seemed to get stronger every year.

In 2025, he set four American records on the road — 20 kilometers (twice), half-marathon, marathon; claimed three consecutive victories in major road races, including the U.S. 20K championships; and placed fourth in two of the world’s most prestigious marathons — Boston and Chicago.

In the latter, he broke a 22-year-old American record by almost a minute, clocking a time of 2:04:43.

“I don’t know if there’s been a better year for an American for a long time,” Eyestone said at the end of the year.

He will be conspicuously absent in Boston.

Mantz’s training partner, Clayton Young, another former BYU NCAA champion and Olympian, will compete in Boston, as planned, but he too has had what Eyestone calls a few “hiccups” in his training build.