The Seattle Mariners have had some of the best pitching depth in Major League Baseball the last few seasons. That has been thanks to a farm system that has produced some talented starting pitchers as well as a player development system that has churned out lights out relievers. The Mariners need to stock up on some more starting pitching depth because they traded Marco Gonzales earlier this offseason.
The Mariners were incredibly lucky in 2022 to make it through nearly the whole season with a solid five starting pitchers. We saw in 2023 that due to injuries and lack of perfomance, the Mariners need to have backup plan upon backup plan for their starting rotation. Bryce Miller and Bryan Woo were incredibly important to Seattle in 2023, but the club can't bet their season on those two pitching 200 innings because they have never done it before.
If the Mariners plan on having Luis Castillo, George Kirby, Logan Gilbert, Bryce Miller, and Bryan Woo pitch 180 or more each then they will almost certainly be sorely mistaken. The Mariners need more options for the back end of their rotation and if they start with Woo or Miller in the minors then they could have them ready to fill in if there is an injury. Here are three starting pitchers who could be back end or depth options for the Mariners in 2023.
1. Michael Kopech
Michael Kopech was once an elite starting pitching prospect. Unfortunately, it has never all come together for the tall right-hander. He has had multiple injuries that have effected his young career. He made his big league debut in 2018 at the age of 22. He pitched less than 15 innings at the MLB level that year and would not make it back to the bigs until his age 25 season.
The last two seasons Kopech has had less injury problems and has pitched 119 and 129 innings. There are some good tools here with the former top prospect. He has a fastball that averages just over 95 miles per hour. He uses that fastball a lot, over 60% of the time in 2023. His top secondary pitch is a slider that he threw as high primary second pitch. He also has a changeup and curveball that he threw less than 12% combined last year.
He also gets a lot of extension because of his long 6-foot-3 frame. Who else gets a ton of extension on their release? Mariners righty Logan Gilbert. If the Mariners can make a tweak on the slider with Kopech and work with him on where to throw the fastball to avoid damage, or maybe add a two-seamer like some of the other Seattle starters have, then they could have an improved starter on their hands.
The Chicago White Sox are likely looking at rebuilding this offseason after a very disappointing 2023 season. A lot went wrong for them last year and maybe getting to an organization that has helped pitchers improve could work wonders for Michael Kopech who will turn 28 in late April.
He is the one pitcher on this list who is not a free agent and would have to be acquired via trade. The trade cost is a lot less than it would have been four years ago, and I think the Mariners could offer some things to the White Sox that they don't currently have in their farm system. The White Sox don't have an outfield prospect inside their top 15 prospects according to MLB Pipeline. The Mariners could offer Zach DeLoach and Prelander Berroa to give the White Sox help in their outfield for next season and years to come and a high risk high reward reliever for two years of Kopech in arbitration.
2. Sean Manaea
Sean Manaea once was a quality starter for the Oakland A's and was a big part of their competitive window at the end of the 2010s. As he has gotten older he has not been as effective as he was several years ago. He spent last season as a swing man with the San Francisco Giants and could be a valuable piece for the Mariners overall pitching staff in 2024.
Last year the tall lefty started ten games and made 27 appearances out of the bullpen for the Giants. He did not just lose his starting rotation spot due to poor performance part way through the season. Manaea bounced back and forth between the rotation and the bullpen for the whole season. He had multiple five and six inning starts and even had a seven inning start in September against the Dodgers.
The Mariners could easily add Sean Manaea to their roster for next year. He signed a one year contract last season for $10 million. He could probably be had for a similar contract again this year, maybe even a little less. A one year deal with the Mariners pitching development group could give Manaea a great opportunity to start early in the year and move to the bullpen.
3. Frankie Montas
Frankie Montas also used to be a front of the rotation of those competitive A's teams. After a 4 fWAR season in 2021, Montas had a good first half of the 2022 season before getting traded to the New York Yankees and then falling off due to shoulder injuries.
The former A's started only pitched 1.1 innings last season and that came on September 30 for the Yankees. He missed nearly all season recovering from the right shoulder injury that derailed his 2022 season. He was thought to be a Luis Castillo equivalent at the 2022 trade deadline, and the Mariners can't be more excited that they traded for Castillo and not Montas.
The Mariners now have the chance to add Montas to their roster at a significant discount. With the Mariners seemingly hamstrung by payroll restrictions from the ownership group, Jerry Dipoto has to do his best to shop in the bargain bin. Montas certainly is in the market to rebuild his value so a one year contract for $5 million or less would probably get the righty who will pitch next season at the age of 31.
All of these players could serve similar roles for the Mariners. They could be a back end of the rotation starting pitcher or they could pitch out of the bullpen. With financial limitations seeming to hold back the plans of the front office, adding quality depth at starting pitcher is important for this team in 2024.