Boston Marathon winner Meb Keflezighi says he lost his running shoe deal with Nike three years ago because of his age.

The 38-year-old distance runner signed a new shoe deal three years ago with Skechers, a footwear company more known for casual "lifestyle" shoes than hard-core running gear, after Nike dropped Keflezighi from its endorsement roster.

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During an interview with CNBC on Tuesday, Keflezighi said his deal with Skechers has boosted his career and helped his running mechanics.

"I'm almost 39 years old and Nike thought I was probably too old," Keflezighi said on "Squawk on the Street." "And with the Skechers partnership, things have been going really well."

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Keflezighi won Monday's marathon with a personal best of 2:08:37, becoming the first American male to win the Boston Marathon since 1983. He won the New York City marathon in 2009. According to NBC Sports, Keflezighi went seven months without a shoe contract before Skechers need a pitchman for its first-ever running shoe line.

A Nike spokeswoman declined to comment on Keflezighi's assertions.

—By CNBC's Jeff Morganteen