Paxton, a rookie who moved to 4-1 on the season after throwing 6 2-3 scoreless innings on Tuesday, will rejoin the Mariners when rosters expand on Sept. 1. He is scheduled to make his next start on Sept. 2 in Oakland.
Ramirez got the nod Wednesday after the Mariners altered their rotation to add extra rest after Thursday's day off.
It is the sixth stint with the big league club for the right-hander this season. Ramirez is 1-5 with a 4.06 ERA in 14 starts, but Seattle manager Lloyd McClendon said his improvement in Triple-A could earn him another outing in September.
"I've seen a lot of growth," McClendon said. "I think the command of the fastball is a lot better, his secondary stuff is much more crisp. I don't think he's pitching away from bats anymore. He's making quality pitches with two strikes."