The Red Sox have activated right-hander Isaiah Campbell from the 15-day injured list and optioned the reliever to Triple-A Worcester, the club announced Thursday.

Campbell was the first player acquired by the Red Sox under new chief baseball officer Craig Breslow last offseason, coming to Boston from Seattle in exchange for infielder Luis Urias. Campbell enjoyed a highly successful rookie season with the Mariners, posting a 2.83 ERA in 27 games, and this year got off to a great start, making nine scoreless appearances during spring training before starting the regular season with one run allowed over his first five outings.

Then Campbell ran into trouble, allowing eight runs over two innings over back-to-back days against the Baltimore Orioles. That ballooned his ERA for the season to 12.79 and he was subsequently placed on the IL with a right shoulder impingement.

Since he began ramping up Campbell has made six rehab appearances for the WooSox, going 6.1 innings without allowing an earned run. He’ll now remain in the WooSox bullpen until the Red Sox call his number again at some point in the future.