What's Up With The Diamondbacks Bullpen?

• Point. The Diamondbacks' bullpen has an overall ERA of 2.58. third-best in the National League.
• Counterpoint. They have struggled in "late and close" situations: All Arizona pitchers have allowed a line of .294/.354/.465 there, the resulting .820 OPS being third-worst in the NL.
• Point. We're 8-1 when leading after the seventh inning, so it's not like the bullpen has cost us many games.
• Counterpoint.. That's down to the offense getting runs after the bullpen coughs up the lead. We have seven blown saves: most in the league, and only four other teams currently have more than TWO.

After the last series, where we blew leads in the eighth or ninth inning every game, I imagine most fans are leaning toward the pessimistic side, even if the final results weren't too bad. But let's take a look at each member of our relief corps, pick out a significant statistic for each, and see how they have done so far this year.

Heath Bell: 14:1 K:BB ratio

If you showed up late from your Siberian vacation and missed Opening Day, you'd think Bell has been close to the best pitcher in the entire Diamondbacks bullpen: For here's his line, discounting that abomination:
Bell: 7.2 IP, 9 H, 1 R, 1 ER, 0 BB, 13 K, 1.17 ERA
A few too many hits, perhaps, but that's largely accounted for by a BABIP around the .500 mark, which is as sustainable as giving Pablo Sandoval a lifetime pass to your "All You Can Eat" buffet restaurant. That K-rate is very impressive, as is the lack of walks. After the worst conceivable start, Bell deserves credit for rebounding nicely.

Josh Collmenter: 26.0% IF/FB

That's the percentage of fly-balls Collmenter has allowed, which have stayed on the infield - more than twice the National League average of 12%, and only two pitchers with as many innings as Josh (the Cubs Jeff Samardzija and the Giants' Chad Gaudin) have a higher rate of infield flies. That's good, because infield flies are almost always outs - more than 99% of the time last year - and are virtually as "good", in pitching terms, as a strikeout. In 2012, a K was worth -.265 runs, and an infield fly -.268 runs. IF rate is not as predictive as K rate, but Collmenter's career number here is 19%, which suggests he should continue to benefit from generating weak fly-balls to his infield.

David Hernandez: 20.0% HR/FB%

By every other metric, Hernandez is doing well. His K-rate is up (27.7% vs. career 23.0%), his walk-rate is down (8.5% vs. 10.1%) and his opponents' OBP is right in line (.319 vs. 318).. But that home-run rate? DHern's career average before this season was 8.9%. MLB average is 7.6%. Much like BABIP, pitchers don't have much effect on their HR/FB%. To quote Fangraphs, "Pitchers with HR/FB ratios much higher or lower than league average will normally regress towards league average in the future, which will have a corresponding effect on their ERA." That's cause for hope, both for Hernandez and Putz, who has the same 20% rate.

J.J. Putz: 91.4 mph average fastball

Putz's fastball peaked in 2006 with the Mariners, at an average speed of 95.6 mph. Since then, the trend has been generally downward, but there wasn't much difference between its velocity with the Diamondbacks in 2011 (93.0 mph) and 2012 (92.9). This year, however, that hasn't been the case, prompting concern. However, it's worth noting that exactly the same early-season loss of velocity happened to Putz in 2012. Through April 23, his average fastball was 91.4 mph too. and the results were similar, a 5.40 ERA. If that pattern holds, we've got four or five more wobbly outings before he returns to form and speed. Maybe he does need more work in spring training?

Matt Reynolds: two saves

Coming in to this season, Reynolds had zero career saves in 165 appearances. Hell, coming in to this week, Reynolds had zero career saves. However, needs must: the two extra inning leads on Tuesday and yesterday, resulted in him now having one less than team leader Putz. His 11.1 inning scoreless streak is the fifth-best by a D-backs reliever to start the season: six more would take him past Lance Cormier's 2005 franchise record. Like Bell, he's getting into Gibby's good books by not walking people - one to date - and has been even tougher on right-handed batters than lefties, the former being 2-for-21 thus far. But with a .154 BABIP, regression will happen.

Tony Sipp: .308 BA vs. LHB

Inevitably at this point of the year. we're still talking about an extremely small sample - only 16 plate-appearances, so with all these stats, caution should be your watchword. But thus far, Sipp hasn't been what we'd hope against left-handed hitters, who have put up a line of .308/.400/.462 against him. Indeed, he has been rather more effective against righties, who are 1-for-9 with five strikeouts, and his overall K-rate, 34.6%, also bodes well - he currently leads the team in relief fWAR. Mind you, we shouldn't expect an enormous platoon split from him in the longer-term, since his OPS against, is almost identical regardless of whether he is facing RHB or LHB (.717 vs. .711).

Brad Ziegler: 14 appearances

Since the start of last year, no pitcher in baseball has appeared in as many games as Ziegler's 91. He's currently on pace to appear in 108 games: unlikely to happen, considering only one pitcher has ever reached 95 (Mike Marshall, who played 106 times for the 1974 Dodgers, winning 15 games and throwing over 200 innings without a single start, on his way to the Cy Young!). Ziegler's workload has been helped by the fact that three of those 14 outings have required him to throw exactly one pitch, and of course, Ziegler's gonna Ziegle. Of his 49 plate-appearances this year, five have resulted in fly-balls. But only one double-play so far? Sheesh...

Going forward

It has certainly been a stressful few days for Arizona fans, and the emotional scars which have resulted, will likely need time to heal. And there is some genuine cause for concern - I'll be a lot happier if/when Putz is regularly back in the 93 mph range with his fastball. But the good news is, a lot of the recent struggles should probably sort themselves out, sooner or later; in particular, fly-balls will stop leaving the park at such an excessive rate, for both JJ and Dhern. Naturally, there will be regression on the other side - Reynolds won't keep that BABIP for ever. But I'd take a few more hits allowed on that end, if that is balanced by a few less home-runs in the ninth inning.