Prospect piece in Mariners' Luis Castillo trade feels too good to be true

The Mariners accomplished one of their main goals ahead of the trade deadline, in being able to ship Luis Castillo and the remainder of his salary to the White Sox. They might have also found a useful reliever in Seranthony Domínguez, while perhaps Nolan Jones has a repeat of his 2023 season somewhere inside of him. Best of all though was snagging Boston Smith, who makes for an intriguing prospect.

It's one thing to rid yourselves of the albatross that was Castillo's remaining salary, something which critics understandably contended could be hard to do. However, to also get what is a legitimate prospect is the cherry on the cake, offering yet more proof of Jerry Dipoto's ability to work magic. So what gives, with a prospect who was immediately ranked at No. 14 in the Mariners' farm system?

Smith was undrafted in 2024, which presented a prime opportunity to show how he deals with adversity. The response was tremendous as he hit a school record 26 home runs the following season with Wright State University, on the way to a 1.269 OPS in 59 games. He was rewarded by being taken in the sixth round of the 2025 draft by the Nationals.

The Dayton, Ohio native didn't get the chance to show the Nationals organization what he could do in a professional game, before being traded to the White Sox in late March this year. Irrespective of where he was though, the next dose of adversity came in wondering if he would succeed in the minors? A lot of this doubt centered around his success in college being achieved in the lowly Horizon League.

A quick rise through the minors for Boston Smith, but it hasn't been entirely smooth sailing

Well, Smith only lasted eight games in Single-A Kannapolis, before the White Sox organization believed they had seen enough to promote him to High-A Winston-Salem. He reacted very well to this, hitting .288 with 14 home runs and a 1.044 OPS over 48 games. The result was being called up to Double-A Birmingham at the beginning of July, to continue his whirlwind rise through the minors.

Impressively, the 23-year-old's productivity was even better in Birmingham over 23 games, batting .306 with eight homers and a 1.151 OPS. As per Keith Law of The Athletic however, he has struggled with offspeed stuff in Double-A by missing 42 percent of the time swinging at anything that isn’t a fastball. As much as this type of issue can be expected when faced against a higher level of competition, Law cites it as something which might have persuaded the White Soz to sell high on him.

Despite this potential issue, it didn't stop the Mariners taking Smith in the Castillo trade. There's just too much to like about a player with his type of power, combined with excellent patience at the plate. Further, while he's currently projected as a catcher, his athleticism and above-average speed open the door for a potential future in either the infield or outfield, where he has seen playing time at a variety of positions in college and the minors.

Overall, even allowing for any concerns, we're still pleasantly surprised the White Sox traded Smith to the Mariners. Heck, he was just named Birmingham Barons Player of the Month for July. Perhaps Chicago know something no one else does, and we appreciate he's not a sure thing by any stretch, but ultimately he's a real bonafide prospect.

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