It's never too early in the offseason to get the trade juices flowing. In a rare and surprising November trade, the St. Louis Cardinals have acquired minor league RHP Riley O'Brien from the Seattle Mariners, according to Derrick Goold.

Although the World Series felt like it was just yesterday, the timing on the trade between the Mariners and the Cardinals was important, as O'Brien was set to enter free agency. Although O'Brien only pitched one inning during his time in Seattle in the 2022 season with the Mariners (he gave up a hit, a walk, and recorded a strikeout), he was a Pacific Coast League All-Star last season. O'Brien was one of two relievers to make the All-Star team.

Despite pitching well and recording a high strikeout rate, the Mariners likely didn't view O'Brien as a priority. He isn't listed in the club's Top-30 prospects, according to MLB.com, and this was far and away his best season in AAA.

RHP Riley O'Brien scouting breakdown

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Perhaps the Cardinals see something worth developing in O'Brien. Here's the Baseball America breakdown on O'Brien from 2021.

“O'Brien's 91-95 mph fastball is above-average and flashes plus. He can elevate for swings and misses and tops out at 97. His slider flashes plus as well, but it's erratic. O'Brien's control has been fringe-average, but his command is below-average. His changeup has never really developed.”

As of yet, there's been no compensation update for what Seattle received in exchange for trading O'Brien to the Cardinals.  St. Louis had the 8th highest bullpen ERA last year in the Majors, so perhaps Riley O'Brien could eventually claim a role if he performs well during Spring Training.