When J.J. Putz was sent to the Disabled List with elbow soreness, any replacement was always considered temporary. It would be unlikely for the closer of the past couple years to lose his job unless the replacement dominated. Heath Bell has achieved the end results for the most part, but after giving up 5 home runs in as many appearances, his utility lessens.
Pinpointing Bell's problem isn't as simple as pointing to any particular number. His strikeouts per 9 innings is more in line with his classic San Diego days, and walks are at a similar rate. His line drive rate is up at the expense of groundballs and flyballs. And although the advanced metrics of FIP, ERA-, and FIP- all suggest he's having a bad season, this is likely caused mostly by his tremendous home run rate.
Since 2007 Heath Bell has never had a HR per 9 rate above 1 for a season, even during last year's tire fire. This year his rate is 2.20, meaning a little more than 2 home runs every 9 innings pitched. To put that in comparison, only David Hernandez and J.J. Putz have a HR/9 rate above 1.0 for D-backs relievers this year (and Putz has a nearly identical rate).
There is some reason to believe that the rate is a quirk and isn't the new reality. Before the recent spate of home runs, his HR/9 was .76. So what has he been doing differently? Well, nothing, really. All 5 of the home runs given up in the recent run have come off his 4 seam fastball, yet that same pitch has a higher velocity and better horizontal movement this month than in prior months. But if you compare the movement to his halcyon years, the change is stark, to the tune of a couple inches.
Essentially, his pitches have flattened out, and if he's thrown better pitches this month, the results haven't borne this. Batters have watched film and can see that he doesn't have the same stuff. And since he throws his 4 seamer 72% of the time this season, it's not difficult to sit on it and then tee off. On top of the 5 home runs, his batting average against on the fastball this season is .357, and the slugging is .653.
So to ask the titular question: if not Heath Bell, then whom?
There aren't that many good answer. David Hernandez would have been the People's Champion last year or the year before, but this year sees a variety of issues that, although not as severe as Bell, could still be dangerous in the closer position. His K, BB, and home run rates are all moving in the wrong direction. Digging into velocity and movement, however, it might not be so bad. His velocity is up, and so his movement on the fastball, and it seems that when he screws around with his curve is when he gets into trouble.
With Matt Reynold on the DL, Brad Ziegler might be the only real other choice for closer. Even though he's probably best as an escape artist and righty specialist, the lack of other choices is forcing me to consider him. The overall numbers for Ziegler look good and in line with his career, and he isn't prone to giving up the home run. Yet his groundout game is still probably more useful to bring into high leverage situations with men on base, instead of being wasted in the traditional 'bring in the closer in the start of the 9th.'
Of the 40 appearances Ziegler has made this year, 26 have been in high or medium leverage situations. It seems to his 76.8% groundball rate is too valuable in his current role.
Otherwise, the rest of the bullpen has roles that don't naturally lend to closers. Josh Collmenter has been aces as a long reliever, and given the shakiness of the starting rotation and the D-backs penchant for extra inning games, he probably provides most value there. Tony Sipp has been used against all comers, but he probably should be used as a righty specialist, given that his numbers are significantly better this year against RHB than LHB. And I don't think any trusts Will Harris or Zeke Spruill in the role.
If it were up to me, I'd probably just continue to use Bell and use Hernandez if the situation demands it. Otherwise, we don't have a ton of options short of calling someone up, and the wait might only be a couple more weeks.
What do you think? Who should be the spot closer until Putz gets back?
All stats provided by Fangraphs, Baseball Reference, and Brooks Baseball.