As something of a follow up to roy's post earlier this year, I decided to take a look at the bullpen for the Braves this year. Effective usage of the bullpen can make a huge difference in a team's success. While the Braves made major moves to improve the rotation (which is now the 6th best in the majors in ERA), we never really addressed the bullpen in the offseason. To date, the bullpen has been so-so, posting a great strikeout rate but a league average ERA.

I'm going to take a look at how the Braves have been managing their bullpen using gmLI from FanGraphs. gmLI is the measure of the Leverage Index of the situation when a relief pitcher enters the game. Tom Tango, the creator of Leverage Index, describes Leverage Index as "a measure of the fire the player faces" in any given situation. Using the inning, outs, score, and number of players on base, gmLI can show us which relievers are being put into the most critical situations. Closers, for example, have an extremely high gLI; mop-up relievers will have the lowest. Overall, I was pretty impressed with our bullpen management.

Mike Gonzalez
33 IP, 2.18 ERA (3.37 xFIP), 1.24 WHIP, 11.45 K/9, 3.83 BB/9, 1.6 gmLI
With 8 saves, Gonzalez has performed admirably in the closer's role this year. Coming off a 4.28 ERA last year, many feel that Gonzalez has shown major improvements. The difference has been in his batted ball profile; he's had a nearly nine percent increase in groundball rate and a corresponding decrease in line drive rate. However, I would guess that this is unsustainable. Additionally, Gonzalez (being a flyball pitcher) is benefiting from a 5.7% HR/FB rate. Gonzo was incredible unlucky last year, but very lucky this year; I would expect that his ERA will settle around the mark projected by xFIP.

Rafael Soriano
32.2 IP, 1.36 ERA (2.83 xFIP), 0.98 WHIP, 12.4 K/9, 3.33 BB/9, 1.52 gmLI
While Soriano already has 6 saves, his gmLI suggests that his usage is pretty normal for a set-up man. While Bobby does have a pretty good amount of confidence in him, it seems that he's not quite challenging Gonzalez as a secondary closer. This is a shame, considering he's been better in almost every possible way. I would ideally like to see Soriano become the closer, but at least he should be seeing some more high-leverage action.

Eric O'Flaherty
25.1 IP, 3.91 ERA (4.30 xFIP), 1.07 WHIP, 5.44 K/9, 1.42 BB/9, 1.16 gmLI
This is a considerable gap in confidence between spots two and three in the bullpen. Claimed off waivers last November, O'Flaherty has been a solid addition to the bullpen. O'Flaherty sports an impressive 48% ground ball rate to go along with tight control. He has, however, been the beneficiary of quite a bit of luck as far as home runs go (his 3.7% rate is unsustainable), so expect his ERA to rise a bit.

Peter Moylan
26.2 IP, 4.73 ERA (3.94 xFIP), 1.58 WHIP, 8.10 K/9, 5.74 BB/9, 1.14 gmLI
Moylan has been...well, pretty bad this year. In 2007, Moylan had a 1.80 ERA in over 90 (!) innings of work. Many metrics suggest that 2007 was something of a mirage, though, as Moylan posted a .236 BABIP and a Left on Base % of over 80%. xFIP suggests his true skill level was in more of the 3.75 ERA range, which is still largely true. This year, Moylan has been on the poor end of the luck spectrum. For one, his .328 BABIP seems inflated. However, even skill wise, Moylan seems to have lost something. Even though he is striking out almost 3 more batters per nine innings, he is walking 2.64 more. Wilder and out of control, Moylan has posted a terrible 1.58 WHIP. Moylan seems to have more trouble in the more critical roles; Moylan had a gmLI of only 0.85 in 2007. Moylan will regress a bit to the mean (and is probably better than O'Flaherty), but don't expect him ever to return to his past form.

Jeff Bennett
32.2 IP, 3.03 ERA (4.58 xFIP), 1.84 WHIP, 6.06 K/9, 5.09 BB/9, 1.11 gmLI
The fact that Bennett is being used quite similarly to Moylan and O'Flaherty worries me, because he's considerably worse than both of them. Bennett's ERA is deceptively low; he's bad in almost every possible way. 4.58 may be a harsh indicator of talent, but it is much more accurate than his actual ERA.

Not included (not enough appearances this year): Blaine Boyer, Jorge Campillo, Manny Acosta, Buddy Carlyle.