Our pen couldn't hold down leads for 3 out of the 6 months out of the season. I didn't like some of Ross's pen decisions in April and May, and a few in Sept, but it's not Ross' fault guys got hurt and the FO didn't give him much late-inning pen options or depth or even a clear closer option, or much pen help at the deadline.
Anyways, I do think manager decisions matter over the course of 162 and especially in close games, I think it can absolutely be the difference in a handful of games. It's possible Ross cost them a few games but I don't think he's responsible for the 9-win gap with the Brewers. The Brewers had a fantastic pen to turn tight leads into wins, they didn't need to blow teams out.