I find the Mariners' bullpen confusing. The TV keeps telling me that the bullpen is a team strength, but we've seen Morrow blow three games, we've seen a lot more Denny Stark than any "good bullpen" should be showing, and Mark Lowe has been awesome at times and rather hittable at others.
I wanted to disprove the TV a little bit, so I thought about the bullpen's job. It seems to me that Priority One for any bullpen is, when given the lead, maintain the lead so that your team wins. Priority Two would be something along the lines of, well, when you're not in the lead (or tied), give up as few runs as possible so that your offense has a chance to climb back in it.
I thought what I'd do is take a look at the WPA charts for each game so far and see if the M's have been reasonably successful in games where their WPA reached above 90, 80, and 70. Unfortunately, I think this is some pretty noisy data, because you have games like May 18, when Washburn blew the game and it had nothing to do with the bullpen, or games like the 15-inning affair on May 3 where we never had the lead when we came up to bat (and the bullpen surrendered 3 runs in extras... it's hard to give the 'pen credit for a good job when they do things like that).
What I end up with isn't exactly a good proxy measure for team bullpen usefulness, but I still find it interesting.
The Mariners have won 22 games so far. By definition, their WPA reached above 70, 80, and 90 in these games.
The M's are 22-3 in games where WPA was at one point 90 or above: April 7, May 14, and May 26.
The M's are 22-9 in games where WPA reached 80 or above, including the games listed above and also April 29, May 2, May 5, May 13, May 18, and May 23.
Finally, the M's are 22-11 in games where WPA reached 70 or above, including the games already mentioned and April 16 and May 9.
Now for some math. The M's played 25 games where WPA > 90.We'd expect them to win 90% of those games. 90% of 25 is 22.5, so we're only .5 games under that. That strikes me as okay, but nothing special.
31 games where WPA > 80, and 80% of 31 is 24.8, which is 2.8 games more than actual. Looks like we've been having a little trouble here.
33 games where WPA > 70, and 70% of 33 is 23.1, just 1.1 games more than actual, so again, looks like we're okay in this area, but we don't have it on lockdown.
I'm not sure where to take this information from here, especially because the data seems really noisy, but I thought I'd at least put it out there for public consumption.