"He was pretty sick last night, so we're going to hold him out," said manager Lloyd McClendon.
Seager is the third Mariners player to come down with the flu in the past two weeks. Catcher Mike Zunino dealt with a similar illness on the day the team traveled to New York on April 28, though he was able to play the next night against the Yankees.
Pitcher Felix Hernandez lost nine pounds in two days and said he was physically drained in his May 2 start in Houston, when he was only able to go five innings.
Now Seager is temporarily sidelined, which takes one of Seattle's hotter bats out of the lineup. After a slow start, Seager won American League co-Player of the Week honors for April 21-27 and he's batted .340 (18-for-53) with five home runs and 17 RBIs over his last 14 games.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.