Cardinals trade candidate offers a chance for Mariners' Jerry Dipoto to correct a mistake

Leaving aside criticism of how Dan Wilson managed the bullpen on Sunday versus the Guardians, it's clear as day the Mariners need quality reliever reinforcements. And while Aroldis Chapman would be a strong addition in an ideal world, his less-than-ideal past means its unlikely to happen. However, another more underrated option Jerry Dipoto should consider is Riley O'Brien, who was previously with the M's organization.

It's bad enough that the Mariners are already a man short in the bullpen, due to their ongoing use of a piggyback strategy until at least the All-Star break. However, the situation has been made worse by the lack of available options, with Matt Brash, Carlos Vargas and Cooper Criswell all out until August. And while the bullpen for the season as a whole ranks seventh in the majors with a 3.67 ERA, they're 24th with a 5.13 ERA during June.

Something has to give, because the Mariners can't go on like this. General manager Justin Hollander can talk about Brash being almost like a trade acquisition when he returns from injury, but the team still has to make it to Aug. 3 deadline. In this respect O'Brien is an intriguing if unassuming option, with ESPN's Kiley McDaniel and Jeff Passan ranking him as their No. 28 candidate to be moved.

O'Brien will ring a bell with some Mariners fans, given he spent effectively two seasons with the organization in 2022 and 2023. He was awful in Triple-A Tacoma during his first year, as evidenced by a 7.12 ERA and 1.964 WHIP in 36.2 innings. However, he was much better the following year, as he produced a 2.29 ERA and 1.218 WHIP in 55.0 innings.

Riley O'Brien is one who got away from the Mariners, and he has what they desperately need

The 31-year-old only pitched one inning in the Big Leagues during his time in the Pacific Northwest and when the Mariners needed a roster spot in November of 2023, he was traded to the Cardinals for cash considerations. He had a rough first season in St. Louis, but rebounded with a career year in 2025, highlighted by a 1.5 bWAR, 2.06 ERA and 1.146 WHIP in 48.0 innings.

This season has seen O'Brien take a slight step back based on a 3.93 ERA, but he does have a 3.36 FIP which projects to be a career-low, along with a solid 1.165 WHIP. He's out there throwing heat at a career-best 98.3 mph with good control, and ranks in the 93rd percentile in GB%. He's also a very good righty specialist, with a .197 batting average and .542 OPS against right-handed bats.

Still not convinced the Mariners should take a look at O'Brien? Well, the Cardinals made him their full-time closer early this year and he's converted 20 of 24 save chances (one off the NL lead) with just one blown save since May 10, making him at least reliable cover for Andrés Muñoz, who's had a nervy season. On top of this, he's under team control through the 2030 season.

From O'Brien's perspective, a trade to the Mariners would mean returning to the city where he was born, with him also playing at Shorewood High School in Shoreline, Washington. Bringing him back would give Dipoto the chance to correct one of his few mistakes on the pitching front.

Add us as a preferred source on Google

Follow