The raw data
Taken from Baseball Heat Maps, whose spreadsheets extract the information from MLB.com's transaction logs. The only tweak I mage was they has Bronson Arroyo listed with the Diamondbacks for the entire 2015 season, so I amended that to reflect the date of his trade to Atlanta.
|Bronson Arroyo||6/16/2014||9/29/2014||105||15-day||elbow||Tommy John surgery||Right||RHP|
|Patrick Corbin||3/31/2014||9/29/2014||182||15-day||Elbow||Tommy John surgery||LHP|
|David Hernandez||3/31/2014||9/29/2014||182||15-day||elbow ligament||Tommy John surgery||right||RHP|
|Daniel Hudson||3/31/2014||9/1/2014||154||15-day||Elbow||Tommy John surgery||RHP|
|Matt Reynolds||3/31/2014||9/29/2014||182||15-day||Elbow||Tommy John surgery||LHP|
|Mark Trumbo||4/22/2014||7/11/2014||80||15-day||foot||stress fracture||left||LF|
|Name||Start date||End Date||Days on DL||DL type||Location||Injury||Side||Position|
|Bronson Arroyo||4/5/2015||6/20/2015||77||60-day||Elbow||Tommy John Surgery||RHP|
|David Hernandez||4/5/2015||6/7/2015||63||15-day||Elbow||Tommy John Surgery||RHP|
|Jake Lamb||4/19/2015||6/6/2015||48||15-day||foot||stress reaction||Left||3B|
|Oscar Hernandez||4/5/2015||7/4/2015||90||15-day||hamate||Broken bone||left||C|
|Patrick Corbin||4/5/2015||7/4/2015||90||15-day||Elbow||Tommy John Surgery||LHP|
|Tuffy Gosewisch||5/28/2015||10/4/2015||129||15-day||knee ACL||injury||Left||C|
Overall time lost
Even if you just look at raw days lost, it's clear the team was very much more healthy last season. The Padres and Rangers were the only teams to have more DL days than the Diamondbacks in 2014, as we racked up a total of 1,354 - that's the equivalent of more than seven players lost for the entire year. This was reflected in a roster where, on the position player side, Arizona in 2014 had only two players, Aaron Hill and Miguel Montero, reach 120 games played. No other team in the majors that year had less than four. If you don't think that matters, the American League champion Royals had ten.
Last year, things were much more stable, the total lost dropping to 891, a drop of 34% compared to the previous season. We also had six players reach the 120-game mark, with catcher and third-base the only positions without a "regular" occupant. Curiously, it was our masked men who seemed cursed, catchers being responsible for 82% of all position player DL days; Ender Inciarte's hamstring and Jake Lamb's foot were the only other injuries to require time on the disabled list. That's the opposite of 2014 where, outside of the TJ epidemic, it was our pitchers who stayed almost entirely healthy. Yeah, I know: that's a bit "Otherwise, Mrs. Lincoln, how was the play?"
Quantifying the losses
This is a bit of a finger in the air approach, which I'm basically making up as I go along, and which I appreciate is far from perfect, though we're not looking for absolute precision. For players who lost less than half the season, I've taken their value that year, and pro-rated it up to cover the missing time. For players that lost over half the season. I've gone back to the last time they played, pro-rated that up to a full year, and then allocated that appropriately to the time missed. Example: Player X misses two months in 2014 and four in 2015. He was worth 3.0 WAR in 2014. That works out to 4.5 for a full year, so the injury "cost" us 1.5 WAR in 2014 and 3.0 in 2015.
As noted, this is not perfect. This presumes that a player's performance would be exactly what it was pre-injury, discounting any effect of age, etc. It also discounts any impact on a player's production after he returns, e.g. Corbin's value this year was diminished because he was still on a strict pitch-count when he came back. I've also said a team can never get "better" through injury - if a player was below replacement level, that goes in as a zero. I'm calling this the PRAT rule, because it was due to Pacheco, Ross and Trumbo. Though you could make a case that if Cody Ross and Mark Trumbo stayed healthy, we'd never have seen David Peralta and Ender Inciarte...
All that aside, here's what the above tells us about the cost of our DL stints in 2014 compared to 2015. I've used bWAR, and players without major-league experience - Bradley, Burgos and Hernandez - are also set at zero.
|Name||Days||Value||Value lost||Name||Days on DL||Value||Value lost|
|Bronson Arroyo||105||2.5||1.4||Archie Bradley||17||0.0||0.0|
|Eric Chavez||51||0.5||0.2||Archie Bradley||83||0.0||0.0|
|Patrick Corbin||182||2.8||2.8||Bronson Arroyo||77||2.5||1.1|
|David Hernandez||182||0.0||0.0||David Hernandez||63||0.0||0.0|
|Daniel Hudson||154||0.0||0.0||Ender Inciarte||31||5.3||1.1
|Ender Inciarte||7||3.7||0.1||Enrique Burgos||27||0.0||0.0|
|Jordan Pacheco||33||0.0||0.0||Gerald Laird||133||0.0||0.0|
|Cliff Pennington||65||1.6||0.9||Jake Lamb||48||1.7||0.7|
|J.J. Putz||36||0.0||0.0||Jeremy Hellickson||23||0.0||0.0|
|Matt Reynolds||182||1.0||1.0||Oscar Hernandez||90||0.0||0.0|
|Cody Ross||41||0.0||0.0||Patrick Corbin||90||1.3||1.2
|Cody Ross||18||0.0||0.0||Randall Delgado||20||0.9||0.1|
|Mark Trumbo||80||0.0||0.0||Tuffy Gosewisch||129||0.0||0.0|
That's a very big difference. By this process, injuries cost the Diamondbacks close to fourteen wins in 2014, only a bit over four last year - our health was 9.5 wins "better" in 2015. Now, it's worth stressing: we certainly cannot say two-thirds of the improvement this year was simply due to the team's relative lack of injuries. As noted, some of the 2014 problems helped open the door for positive contributions from others, and the gap would certainly have been narrower if not for the PRAT rule. But it' is true that the team was probably fortunate in 2015. While the number of DL stints remained the same, the severity and personnel affected were both significantly less impactful.
If we can certainly hope for that to continue in 2015, that's about all we can do. While we can prepare all we want, and I suspect the significantly younger team we had may well have helped, there is always the risk of freak injuries, such as those suffered by Goldschmidt, Bradley, Marshall, Pollock, Ross, etc. This is why depth is an essential part of any team's preparation, across the board. Injuries are unavoidable, and how you handle them is very important. Although when it comes to your star players, pretty much all you can do is keep your fingers crossed the Wheel O' DL lands somewhere else on the roster.