The acquisition of Castillo from the Rays at the trade deadline was a calculated gamble by GM Jerry Dipoto to gain more long-term security without suffering a drop-off from Kendall Graveman, an impending free agent who was dealt to the Astros. Castillo has more-or-less performed as expected, considering the small sample.
Castillo has one save in 10 outings since joining Seattle, tossing 9 1/3 innings and allowing four earned runs. In total on the year, Castillo has a 2.96 ERA/3.92 FIP in 45 2/3 innings with the Rays and Mariners.
Dugger has bounced back and forth between Tacoma and the bigs this season, his first with the Mariners. The results have been underwhelming at both stops, however. He has a 7.30 ERA in 37 innings in Triple-A and a 6.45 ERA in 22 1/3 innings with the Mariners.