Depending on your metric of choice, the Mariners had one of the best starting rotations in 2024, if not the top staff in baseball. I mean, they accumulated the most innings of any staff (942 2⁄3) and allowed the third-fewest runs (354). That's not only an efficient rotation but a great one. They're a major reason why the Mariners won 85 games last season.
But if you want to look for why Seattle only won 85 games with that behemoth of a rotation, look no further than the lineup. A .219/.300/.367 slash line with a 98 wRC+ in the first half won't get it done, no matter the pitching staff.