Diego Castillo

Castillo opened 2021 in Tampa Bay as the team's primary closer, a role that wasn't planned as the Rays like to mix and match in the ninth inning, but one he held out of necessity due to the vast number of injuries that affected the bullpen early on. He earned 14 saves before the injured Rays relievers got healthy and Tampa Bay surprisingly traded him to Seattle. Castillo logged only two saves in six chances with the Mariners as the third option in their closer committee, but he posted a solid 2.78 ERA and 0.98 WHIP for the season with a career best 32.2% strikeout rate and 7.3% walk rate. His velocity dropped a few ticks to 94.7-mph and he allowed a career worst 1.4 HR/9, but there's still plenty to like in his profile. Castillo will likely get some save chances, but the likelihood of surpassing the 16 saves he logged last season are slim, as Seattle like to use a committee and has a tall high-leverage ladder.

Rays relievers are typically more useful in formats that give some value to bullpen arms beyond just saves, as 12 different Rays picked up a save last season. Castillo was one of the more valuable members of that group regardless of format, as he finished second on the team with four saves while posting a 1.66 ERA in 21.2 innings. His underlying numbers don't back up that level of dominance, as it took a .176 BABIP and an unsustainable 100% strand rate to get him there. His 4.53 FIP, which factors in a decent 25.8 K% and a poor 12.4 BB%, both career worsts, paints a considerably less impressive picture. Small-sample caveats apply to both his ERA and FIP, however, and finishing with a mark in the realm of his 3.30 ERA and 3.53 FIP from his first two years wouldn't be a surprise. That would leave him shy of typical closer material, though the Rays' usage patterns probably mean he'll still get some saves.

Castillo proved to be a jack-of-all-trades for the Rays in 2019, working as both a setup man and closer -- finishing with 17 holds and eight saves -- while also starting six games as an opener. He was dialed in for the first two months of the season before struggling in June and subsequently landing on the injured list with a shoulder issue. Castillo returned after the All-Star break and showed no ill effects, posting a 2.88 ERA and 1.17 WHIP over 34.1 second-half innings with a 43:10 K:BB and 0.8 HR/9 over that stretch. His skill set, which includes a fastball that touches triple digits with a swing-and-miss slider, is reminiscent of a closer; while Emilio Pagan was traded, the Rays used a committee at times and could do so again in 2020 as they still have a plethora of viable endgame options. Either way, Castillo should see high-leverage work and is a good bet to see at least some save chances.

Castillo posted strong numbers in his debut campaign, recording a 3.18 ERA backed up by a strong 29.3% strikeout rate. He technically logged 11 starts, though all came firmly in the "opener" role, as none lasted more than two innings. With a 98-mph fastball, an 89-mph slider and a strong minor-league track record, Castillo's performance looks legitimate and repeatable. He has the skill set to eventually get a look in the closer role. The team may prefer his flexibility and willingness to work in the opener role for the time being. The job exposes him to the toughest part of the opposing order more often and hurts his chances for wins, but also gives him to a larger workload than is typical for a reliever -- he worked 1.3 innings per outing last season -- which helps him rack up more strikeouts.