By trading three of their top relievers in the month prior to Monday¡¯s Trade Deadline, the Orioles turned the tangible steps forward their bullpen showed this season into part of their rebuilding plan. The latest example came minutes before Monday¡¯s 4 p.m. ET deadline, when Baltimore dealt right-hander Miguel Castro to the Mets for left-handed pitching prospect Kevin Smith, plus a player to be named later or cash.

The deal concluded a busy trade season for the Orioles that saw them move Mychal Givens, Richard Bleier, Castro and two other members of their pitching staff for a bundle of prospects.

TRADE DETAILS
Orioles get: LHP Kevin Smith
Mets get: RHP Miguel Castro

The Orioles open a two-game series against the Mets on Tuesday.

¡°I spent four great seasons here. I will miss everything about it,¡± Castro said through team interpreter Ram¨®n Alarc¨®n. ¡°It¡¯s going to be exciting to face my teammates, but also at the same time it¡¯s going to be difficult. I¡¯ve spent so much time with them, bonded with them, so it¡¯s definitely something strange and weird. I am looking forward to it.¡±

In Smith, the Orioles acquired New York¡¯s No. 12 prospect, per MLB Pipeline, a 6-foot-5 left-handed starter who reached Double-A last season. He was New York¡¯s seventh-round pick out of the University of Georgia in 2018, then posted a 3.15 ERA with 130 strikeouts in 117 innings across two levels in 2019. Smith enters Baltimore¡¯s system as its No. 12-ranked prospect, per MLB Pipeline.

Smith, 23, creates natural deception with his pitches due to his size, frame and delivery. He features a three-pitch mix: a high-spin fastball that sits in the low 90s, a swing-and-miss slider and a developing change. He is the sixth prospect the Orioles netted in the 48 hours prior to the Deadline, having traded longtime setup man Givens to the Rockies and veteran lefty Tommy Milone to the Braves on Sunday.

In sum, Baltimore made five deals in the past calendar month, parting ways with Givens, Castro, Milone, Richard Bleier (to the Marlins) and Hector Vel¨¢zquez (to the Astros). They received nine prospects in return: bat-first infielders Tyler Nevin and Terrin Vavra from Colorado, upside lefty Smith from the Mets, and six players to be named later.

This year, teams can only trade players who are part of their 60-man player pool, but were permitted to include players to be named later in trades. Though there are exceptions, by and large teams across the league included two types of prospects in their pools: those that can help at the big league level soon, and top prospects that are unlikely to be dealt. Organizational prospects in the middle ground -- i.e., those not in pools -- must be given the PTBNL status in the short term.

Vavra slots in as the No. 13 prospect in Baltimore¡¯s system, with Nevin checking in at No. 23, per MLB Pipeline.

One of the Orioles' most durable relievers the past three seasons, Castro appeared to be turning a corner earlier this season by augmenting his plus stuff with improved command. His 4.02 ERA through 16 appearances only tells part of the story; Castro, who throws one of baseball¡¯s hardest sinkers, is also posting career-best strikeout (34.3 percent) and walk (7.1 percent) rates in his age-25 season.

¡°He¡¯s been improving ever since I¡¯ve seen him pitch and was putting together a nice year,¡± manager Brandon Hyde said. ¡°It was tough to say goodbye to him during the game.¡±

All told, Castro went 7-13 with a 4.06 ERA in 183 appearances for Baltimore since being acquired from the Rockies in 2017. This is the third time he¡¯s has been traded in his career.

¡°We think Castro has a high ceiling," said Mets GM Brodie Van Wagenen. "He¡¯s still only 25, and he¡¯s already pitching meaningful games, late in games, and has some years of experience under his belt. We think Kevin has potential. Whenever you have a guy that has potential to be a fifth starter, those guys are valuable, but at the end of the day, we felt like getting the upside for a here/now bullpen arm that can help us was something that we needed to do.¡±