Cardinals Reportedly Land Bullpen Depth In Trade With Mariners In Intriguing Move

The St. Louis Cardinals are getting an early start on offseason additions. 

Major League Baseball's offseason general manager meetings are set to begin Monday and the offseason is upon us. It's expected to be an exciting offseason with a handful of stars expected to change teams. The trade market also is expected to be active. 

While the Cardinals have been linked to top-tier free agent starting pitchers, they have other work to do, as well. St. Louis got an early start Monday by reportedly adding relief pitcher Riley O'Brien in a trade with the Seattle Mariners to boost organizational depth, according to the St. Louis Post-Dispatch's Derrick Goold.

"Cardinals have acquired (right-handed pitcher) Riley O'Brien in a trade with (the Mariners)," Goold said. "A (Pacific Coast League) All-Star, the 28-year reliever had 86 strikeouts and a 2.29 ERA in 55 innings for Mariners' Class AAA team. He was set to become a minor-league free agent."

O'Brien is 28 years old and initially was drafted in the eighth round of the 2017 Major League Baseball June Amateur Draft by the Tampa Bay Rays. This is now the third time O'Brien has been traded in his young professional career. He was traded by Tampa Bay to the Cincinnati Reds in 2020. Cincinnati traded O'Brien to the Mariners in 2022 and now he will join the Cardinals organization. 

The righty made his big league debut with the Reds in 2021 and also made an appearance with the Mariners in 2022. He spent the entire 2023 season with the Triple-A Tacoma Rainiers and impressed with a 2.29 ERA across 51 outings. It's unclear what level he will play in the Cardinals' organization, but he at least provides more depth with big-league upside. 

This is just the beginning of a busy offseason for the Cardinals.