However, it's possible that he could still participate in the upcoming All-Star Game festivities in Denver.
Manager Scott Servais said he couldn't comment on Kikuchi's status "for a number of different reasons," but that he was "not that concerned with where's he's at."
"I still think he's planning on heading over to the All-Star Game," Servais said.
No other details were available about the pitcher's status.
The Mariners promoted promising catching prospect Cal Raleigh to take his place in the lineup. Raleigh will make his debut later Sunday against the Los Angeles Angels. He'll catch a bullpen day from the Mariners staff.
Kikuchi has been one of the top left-handers in baseball this season, his third since signing with the Mariners and moving over to the major leagues from Japan. He's 6-4 with a 3.48 ERA and 98 strikeouts.