New York Mets designate lefty reliever for assignment

Castillo, who last pitched for New York on Friday during their series-opening win against the Giants, was initially traded to the Mets from the Arizona Diamondbacks on May 15 for cash considerations. The lefty seemed to be a solid fit for the bullpen, especially after the Amazins' lost two of their lefty relievers, A.J. Minter (lat strain) and Danny Young (Tommy John), to season-ending surgeries.

In his first 17 appearances for the Mets, Castillo posted a 4.58 ERA with 17 strikeouts across 17.2 innings pitched. However, following a poor outing against the Atlanta Braves on June 24 that raised his ERA to 5.60, the 29-year-old was DFA'd by the Mets on June 25. After clearing waivers, he was sent outright to Triple-A, where he posted a 1.69 ERA in five appearances for the Syracuse Mets.

Castillo returned to the Mets on July 25 and tossed a scoreless ninth inning that night, striking out three batters during New York's 8-1 win against San Francisco. Nonetheless, he was the corresponding move to make space for Soto's arrival to the team.

With Castillo's tenure in Flushing most likely over, the newly acquired Soto joins veteran reliever Brooks Raley as the only two lefties in the Mets' bullpen.

In 19 outings for the Mets this season, Castillo went 0-2 with a 5.30 ERA, 20 strikeouts, and a 1.93 WHIP across 18.2 innings.