I know that ACT, myself and another person (sorry for not remembering who) had a discussion awhile back on Mariano Rivera‘s rWAR. I had asked Tango about it and he explained the difficulty we were having in getting the same numbers thatn Baseball Reference has. There’s a big difference between his fWAR and rWAR and Tango explains why.
Obviously the two are calculated differently and we already knew that, but I figured we needed a new thread and this was a good article to highlight. I know I’ve recently come around to not wanting to use FIP in WAR so rWAR makes more sense to me. FIP is only a subset of what a pitcher does and it ignores everything other than strikeouts, walks and home runs. Yeah, a pitcher has control over those and much less control over the other stuff, but I want my seasonal WAR to be representative of how the pitcher has performed. That performance includes luck. We include it for batters so we may as well do the same for pitchers.
This doesn’t mean FIP is any less useful. It tells us what the pitcher has the most control over and that’s what is important in evaluating future performance.