If predicting the future were easy, then surely at least half of the Baseball Prospectus staff would have seen the Boston Red Sox’ championship season coming. After all, forecasting is a large part of what we do here. Just ask Nate Silver.

Yet for each of the countless variables impacting a player’s statistics, we take solace in the gift of sample size. Over a full season, many fluky statistics tend to stabilize.

Injury risk analysis, however, presents a dilemma. One bone-crushing outfield collision, one awkward dive into the front row, one sticky tract of mud on the pitcher’s mound can derail a ballplayer’s career; even faster his season. Sure, there are Matt Manteis and Rusty Greers, but each year dozens of strapping twenty- and thirty-somethings are introduced to the disabled list for the first time.

It comes with the territory. There’s no nice way to predict someone will get injured, and obviously there’s no flawless way to project how the human body will respond to rehab and treatment. Caveats aside, new tools and technologies are always being developed to help get more accurate information. BP is hard at work on an injury accounting system that will help translate injuries into a win-loss calculation. We’re also trying to increase the transparency for team reports of injuries, both by journalistic pressure and by our valuable team sources. When a team sees an elderly gentleman leaning on a fence at their Florida training facility, they may be seeing one of UTK’s best sources.

Each spring, in Team Health Reports, we use a points system encompassing several factors to quantify injury risk as much as possible. The reports classify players as “red light” (high injury risk), “yellow light” (moderate injury risk) and “green light” (low injury risk).

Now, to be consistent with BP’s approach and use objective, relevant information, it’s time to appraise our methods:

                DL stint    No DL    Total    % of Total
Red lights        37         26       63         59%
Yellow lights     54         93      147         34%
Green lights      81        149      230         35%

Red Lights

A pretty astounding 59% of red-shaded players landed on the disabled list. Several began the year seemingly healthy and later fell victim to their own vulnerability. Remember when the nation was touting Ken Griffey Jr.‘s return to glory? The Astros report cautioned about Wade Miller‘s health concerns before they were obvious to the general public, and he’s still working on a comeback. Preston Wilson earned a red light despite completing a DL-free 2003, then was limited to just 58 games. And just when a healthy Carlos Guillen was putting the finishing touches on his breathtaking breakout year, he was brutally halted by a mid-September ACL tear. Only the expanded rosters kept him off the DL.

There were brighter days, though. Mark Mulder, Jermaine Dye and Barry Larkin logged a total of zero days on the disabled list, thanks in large part to the watchful eye of trainers and medical staff. Trevor Hoffman‘s light was noted as being “reluctant,” but the system had the final word; he remained healthy all year.

There is a clear bias in the data that will need to be accounted for–teams that have significantly lower injury numbers, such as the A’s, tend to throw the light system off. We’ve made an alteration this year that will help account for this by expanding the categories and taking more points off for the top six teams in terms of fewest days lost to injury.

Others were red-lighted with full knowledge they would start the season disabled, recovering from Tommy John surgery. A.J. Burnett missed the first two months but, as expected, returned and was a major contributor. Bob Wickman rejoined Cleveland in early July and was decent out of the pen. If only they were all so easy!

The results for the red light players were strong. Players in this group were 73% more likely to spend time on the disabled list than yellow light players. Red light players are at such an increased risk of injury that any player so marked should be backed up strongly, whether you’re a major league GM or just running a roto team.

Yellow Lights

This was a mixed bag, as it should be. Many of baseball’s best starting pitchers–Randy Johnson, Johan Santana, Ben Sheets, Roger Clemens, Roy Oswalt, Carlos Zambrano–enjoyed healthy seasons. Pedro Martinez was yellow, but with the disclaimer that he was “much less likely than [2003] to come up lame,” and he also averted injury. This doesn’t mean the risk wasn’t there, just that the risk didn’t translate into loss. Remember, risk is not certainty; it’s merely a greater likelihood of an event occurring during a given period.

Mark Prior and Kerry Wood were not so fortunate, as whispers of workload injustice in Wrigleyville still linger. On the Southside, Esteban Loaiza fell from grace just like the White Sox THR surmised. Javier Vazquez was never shut down, but his previous workload concerns in Montreal were mentioned in the Yankees THR, and he wore down ever so slightly in the second half (6.92 ERA).

One of THR’s loudest victories was Jon Lieber: “He’ll outperform every projection you see on him.” PECOTA had tabbed him for a 5.12 ERA and 4.2 VORP; Lieber posted 4.33 and 27.3, respectively. Lieber’s success contributed to another system change, reducing the points given to a player coming back from Tommy John surgery. Doctors at this year’s ASMI Injuries in Baseball Course surmised that there is a five-year “honeymoon period” after Tommy John surgery. During this period, a player is at reduced risk for another elbow injury. The increased risk of shoulder injury keeps the points there, but the new adjustment should prove more accurate.

Scott Rolen enjoyed an MVP-caliber season until his calf strain sidelined him for most of September (another expanded-roster DL dodger). Among aging catchers, Ivan Rodriguez and Jorge Posada were regarded as good bets to stay healthy despite the yellow, and they did. Gary Sheffield battled thumb, shoulder and stomach woes but somehow played 154 games. The stones thrown at Nomar Garciaparra and Sammy Sosa in Boston and Chicago only added to the sting of their injuries; each was debilitated longer than expected while Vladimir Guerrero‘s core workout regimen kept him nimble enough to bring home the AL MVP.

One final note for yellow lights is that it appears it is in this group where pain tolerance may count for more than in the red or green groups. Many players missed several days or were noted to have injuries yet were not placed on the DL, such as Sheffield. Given the near impossibility of collecting data below the DL threshold, we feel that we may be more accurate in this category than the data indicate.

Green Lights

While the green players hit the disabled list at almost the same rate as the yellow, there were a lot of traumatic/fluke injuries among them. Eric Chavez‘s right hand was crushed by a Damaso Marte pitch. Marcus Giles was sidelined for a couple months after a nasty collision with Andruw Jones. The well documented AstroTurf vs. Joe Mauer face-off ended tragically with Mauer’s handicapped knee casting doubt on his future behind the plate. Magglio Ordonez also collided, with Willie Harris, and the resulting calf strain later gave way to the now infamous bone marrow edema.

For some, subjective evidence suggested more risk, but again, the system reigned. Rocco Baldelli registered as green, but Tampa’s THR came with ample warnings au contraire. The same kid who would be “drastically affected by leg problems” missed more than a month with a quad strain. Worse still, he’ll miss much of the 2005 season with a knee injury.

One particularly nice catch was Carl Pavano, who was tagged green despite a long history of arm troubles. He turned his healthy year into a lucrative contract this offseason.

Plenty of others, not too far removed from injuries, were mild surprises to register at green yet stayed healthy. Adam Eaton is further evidence that Tommy John surgery is becoming more routine. Ron Belliard recovered fully from 2003 back trouble to become an All Star–who knew?

Finally, a confident green light was pinned on Curt Schilling, despite his being 37 and having spent 52 days on the DL the year before. Said Boston’s THR, “Schilling’s season looks worse on the stat line than it does to the medheads…singular injuries are no worse to players the following year than no injury at all.” Of course, he gritted his teeth long enough to pitch nearly 250 innings in 2004, playoffs included.

Final Thoughts

One hindrance in the hindsight analysis of player injuries is the lack of available data. More useful to this study might have been days spent on the disabled list or to look at which injuries were preventable as opposed to traumatic. As we collect better data, we’ll be able to take a closer look at our methods.

The system behind the Team Health Reports is neither perfect nor complete. We’ll continue to look at our results like we look at any performance. We’ll continue to try and assess risk in ways that no other outlet does. Mostly, we’ll keep working hard, collecting data, working our sources and finding the truth.

If information is the currency and power of the digital age, as William Gibson once said, we’re getting richer, but we’re not ready to retire.

Thank you for reading

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