Heading into the offseason, the Seattle Mariners are focusing on bolstering their bullpen, an area identified as a critical positional need. Despite expectations for improvement in 2024, the depth of the relievers remains a concern. The team is optimistic about Matt Brash’s recovery from Tommy John surgery, which is ahead of schedule and expected to see him return early in April. Gregory Santos is also anticipated to be fit after a challenging previous season filled with injuries.

Recently, the Mariners added Shintaro Fujinami to their roster and further strengthened their bullpen by acquiring right-handed reliever Will Klein from the Oakland Athletics in exchange for international slot money, effectively adding him to the 40-man roster. In a corresponding move, left-handed reliever Tyler Jay was designated for assignment. Klein, initially drafted by the Kansas City Royals, had a rocky MLB debut last season with a 6.35 ERA in five appearances, followed by a difficult stint with the Athletics where he posted a staggering 27.00 ERA over three games. While Klein's initial statistics are concerning, the Mariners are known for their capability to develop pitchers, suggesting they might extract better performance from him.