Motter was optioned to Triple-A Tacoma on Wednesday, Corey Brock of The Athletic reports.
The Mariners kept Motter around in case Ichiro Suzuki wasn't ready to go for the start of the season, but with Suzuki being cleared to return, Motter will open the season in the minors. The 28-year-old utility man hit an impressive .350/.427/.640 across 117 plate appearances with Tacoma last season, but he failed to translate that success to the majors, hitting just .198/.257/.326 across 280 plate appearances with the Mariners. Given his versatility, he'll likely be back with the big club at some point in 2018.