Chris Heston's bid to make the Mariners' Opening Day rotation came up short.
The former Giants pitcher was optioned to Triple-A Tacoma on Sunday morning, Seattle announced.
Traded by San Francisco to Seattle in December, Heston struggled in his first spring with the Mariners. The 28-year-old allowed 14 hits and nine earned runs in 11.2 innings over five appearances.
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Heston, who was a major part of the Giants rotation in 2015, pitched in 38 games over three seasons in San Francisco. He compiled a 4.16 ERA and struck out 148 batters in 188 innings.
The highlight of Heston's time with the Giants came on June 9, 2015 when he no-hit the the Mets in New York. He struck out 11 and walked none, but hit three batters.
In addtion to Heston, the Mariners also re-assigned former Giants reliever Jean Machi and former A's pitcher Cody Martin.