The 2025 season was a historic one for the Seattle Mariners. They were able to reach the ALCS for the first time in 25 years and claimed the AL West title. Building one of the most formidable pitching staffs in baseball. They have a core of superstars tied to long-term deals and one of the strongest farm systems in the league. However, this team is not perfect. They will have to improve on all phases of the game if they want to make the leap to a maiden World Series berth. In this article, we identify statistical margins where the Mariners must improve in 2026.
Batting: Power Without Consistent Contact
Contact Quality vs. Contact Volume
The Seattle Mariners were one of the most explosive offenses in baseball. They were third in home runs and in wRC+ behind only the Yankees and Dodgers in both categories. When we have been so accustomed to Seattle being carried by its pitching, in 2025, it was the offense’s turn to carry the load. The lineup benefited greatly from a more aggressive approach installed by renowned hitting coach Kevin Seitzer and Mariners legend Edgar Martinez. Their philosophical impact was immediate and evident.
BIG DUMPER FOR THE LEAD! đź”±
Cal Raleigh’s 43rd home run of the season gives the Mariners their first lead of the night heading into the 9th!
(via @MLB)pic.twitter.com/E9xOOwdFmc
— FOX Sports: MLB (@MLBONFOX) August 9, 2025
However, this was not an offense without flaws, and we can identify where this coaching team will look to improve this offseason. The Mariners, despite their improvements, were an inconsistent unit that could go weeks drastically underperforming. While they had one of the highest ceilings of any unit in baseball, their floor could also be one of the lowest.
We can see this play out in several statistical categories; even with this new aggressive approach, they still struggled to make contact on pitches in the zone. Their Zone Contact% was MLB’s lowest at 80.2%, while the whiff rate ranked third-highest in the league at 28.6%. The total number of zone swings and misses, and the overall miss rate, were both MLB highs at 1,636 and 19.8%, respectively.
This profile limited the Mariners’ ability to consistently move runners and apply pressure to opposing pitching units. It led to missed opportunities to put away hittable pitches and convert runs. This is an issue that became even more pronounced in run-scoring situations.
Performance in Run-Scoring Situations
Their batting average with runners in scoring position (RISP) ranked in the bottom five of the league at .235, paired with an MLB-low RISP BABIP of .268. Their overall performance in those situations was still above league average, posting a 108 wRC+. The underlying production suggests Seattle was able to be aggressive and generate home runs, meaning the issue was not quality of contact, but rather a lack of consistent contact volume.
In 2026, the Mariners will need to become more contact-oriented while continuing to capitalize on their plus power to improve as a unit. Turning solo home runs into more game-changing and impactful homers would elevate this offense to another level. Improving contact efficiency on pitches in the zone would allow Seattle’s power profile to play more consistently, particularly in run-scoring situations.
Pitching: Dominance Early, Diminishing Returns Late
The Seattle Mariners have boasted one of the best starting rotations for the past few seasons, with all five starters carrying ace or No. 2 starter potential. However, while 2025 was by no means a bad season, it was certainly a step down from where the rotation had been in 2023 and 2024. That can be attributed in part to injuries, but even after extended stretches of playing time, all starters apart from Bryan Woo experienced periods of inconsistency. This inconsistency was not only month to month or week to week, but also within games themselves.
The talent level and raw stuff of every member of Seattle’s rotation remain elite. Each pitcher is unique, and when they are on song, they can be extremely difficult to hit. But they often struggled to maintain this level throughout the start, with high pitch counts and long innings, often resulting in short outings or a decline in performance.
That pattern showed up most clearly when examining performance by times through the order. The Mariners were among the league’s best the first time through the lineup, ranking fourth in strikeout-minus-walk rate at 16.1%. Opponents walked just 7.6% of the time, the second-lowest rate in MLB, while Seattle’s starters posted a 3.80 xFIP, third-best overall. That effectiveness largely held on the second pass through the lineup, with a 15.9% K-BB% that again ranked fourth league-wide. Walks remained under control at 6.9%, and the 3.92 xFIP still placed Seattle third in MLB.
Times Through the Order and Workload Stress
The drop-off became more noticeable the third time through the lineup. K-BB% dipped to 14.3%, the walk rate climbed to 7.7%, and xFIP rose to 4.50, sliding Seattle to 17th in the league in that split. The starters also posted a league-best 1.09 WHIP the first time through the order, which dropped to 16th by the third time through.
This is not significant enough to label Seattle a poor pitching unit. It is, however, a clear sign that hitters found it much easier to attack the Mariners’ starters after the first two times through the order. With injuries plaguing much of the rotation, the front office will hope an offseason focused on rebuilding strength and durability can help restore consistency. That will be particularly important for Logan Gilbert and George Kirby, who remain central to the Mariners’ rotation.
But this is not an easy fix. For example, we saw with Kirby that he was forced to lower his arm angle as a result of his shoulder injury and lost some command as a result after returning from injury. This is something that can be rehabilitated through an off-season, or it could have altered his pitching mechanics forever. Only time will tell.
Fielding: Turning Balls in Play Into Outs
Simply put, the Mariners were one of the worst fielding units in the league last season. Across a range of statistical categories, the Mariners ranked amongst the worst in baseball. Even with outstanding outliers such as Rodriguez in center and Raleigh behind the plate. The corner outfield spots and entire infield unit must improve next season. Much of that deficit came on balls in play getting through the infield and shallow outfield, where limited range and arm strength reduced Seattle’s ability to convert routine outs.
Seattle’s defensive issues consistently appeared across multiple tracking systems, rather than in any single metric. Outs Above Average sat at –30, placing the Mariners in the bottom four league-wide, while Statcast range graded out at –23, also bottom four. Arm value was even more concerning, ranking second-worst in MLB at –9. FanGraphs’ composite defensive metric likewise placed Seattle in the bottom five overall. This is something that cannot be fixed overnight and is a result of an aging squad that, while still valuable at the plate. Their best day in the field are certainly behind them. Defensive inefficiency extended innings, inflated pitch counts, and placed additional strain on the rotation and bullpen over the course of games and series.
The Mariners’ pitching staff focuses on throwing strikes and inducing more ground balls, so a surer infield is a necessity. This is why Brendan Donovan has been such an obvious trade candidate and why they were never really in the market for the Japanese hitters, preferring to give an opportunity to both Ben Williamson and Colt Emerson. An injection of youth will hopefully raise the floor and allow the Mariners statistical numbers to improve in 2026.
Conclusion
The Mariners had an outstanding 2025 season and have a strong platform for 2026, but sustaining contention will require more than simple roster additions. Improving contact efficiency, managing starter workload deeper into games, and converting more balls in play into outs are marginal gains that compound over a full season. Addressing these areas would not fundamentally change the Mariners’ identity, but it would make a good team better equipped to improve in 2026.
Top Image Credit: Â Junfu Han / USA TODAY NETWORK via Imagn Images