It took a few months, but the Mariners really got their bullpen into solid shape towards the end of the regular season. From September through to the final game, Mariners relievers combined for a 3.12 ERA (6th in MLB) and a 2.88 FIP (2nd in MLB). It was a point of weakness that the organization seemingly failed to cover at the trade deadline, but based on their recent performance, it seems like the front office knew best all along.
One might assume that much of this success is due to marquee names like Andrés Muñoz and Matt Brash, but other arms have stepped up in big ways this season.