Santiago is the first and only pitcher so far to be ejected and subsequently suspended after Major League Baseball's crackdown on pitchers using sticky substances on baseballs.
The Mariners will not be able to fill Santiago's roster spot for the entirety of his 10-game suspension, per MLB's rules on pitchers using foreign substances.
Santiago was thrown out of the Mariners' 3-2 victory over the Chicago White Sox on June 26 in the fifth inning as he was being pulled from the game and the umpires inspected his glove on the way to the dugout.
Santiago later admitted he used rosin on his glove side, which is in violation of the foreign-substance rule. He was suspended two days later and immediately appealed the penalty.
MLB rules state the umpire will be the "sole judge" on whether any portion of the foreign-substance rule has been violated.
Santiago made three appearances while he was appealing the suspension, allowing four earned runs in 7⅓ innings. For the season, he is 1-1 with a 3.33 ERA in 24⅓ innings over 12 appearances.