On Tuesday night, word went around: Reds starter Bronson Arroyo was working on a no-hitter against the Brewers. Through 7 1/3 innings, Arroyo had allowed only one baserunner, keeping the Brewers at bay after hitting Ryan Braun with a pitch in the first. Milwaukee had managed to get only four balls out of the infield.

This was unexpected, to say the least. Seventy-three pitchers have pitched at least 250 innings over the past two seasons. Only four of them have given up hits at a higher rate than Arroyo. The 35-year-old right-hander hasn’t thrown a pitch at 90 miles per hour all season, and his career ERA is just 3 percent lower than league average. Even if he did throw a no-hitter, no one would say he had no-hit stuff.

That’s why it wasn’t shocking when it all came apart for Arroyo with one out in the eighth. After a walk to George Kottaras, Arroyo allowed back-to-back doubles, then a single. Just like that, the Reds’ 3-0 lead at the start of the inning was erased, and Arroyo’s night was over. His totals: 7 2/3 innings, three hits, three earned runs, one walk, four strikeouts. A strong line, but not one that would suggest Arroyo had flirted with history.

It’s appropriate that Arroyo’s outing ended up looking unremarkable, since one could say the same about most of his starts. But there is one respect in which Arroyo stands out: he’s very, very good at showing up for work.

Baseball Prospectus keeps complete records of major-league disabled list stints, starting in 2002. Since then, 10 pitchers have thrown at least 1,000 innings without once appearing on the DL. Arroyo ranks fourth, with more than 1,800.



Mark Buehrle


Livan Hernandez


Derek Lowe


Bronson Arroyo


Dan Haren


Justin Verlander


Matt Cain


James Shields


Tim Lincecum


Gavin Floyd


Some of these starters are stars, and others are barely above average. But even the less talented ones have accumulated plenty of value, purely by virtue of their unflagging ability to take the ball.

Consider the case of Livan Hernandez, who’s in his 17th big-league season and has yet to spend a day on the DL. In his prime seasons of 2000-2005, Hernandez’ 4.01 ERA was just 5 percent below league average. Forty pitchers averaged at least 100 innings per season over the same span with better ERAs. But Hernandez was the 10th-most-valuable pitcher over that period, racking up over 19 wins above replacement. The nine names ahead of him read like a who’s who of elite pitchers at the start of the century: Johnson, Martinez, Schilling, Clemens, Vazquez, Mussina, Pettitte, Maddux, Schmidt. So how did Hernandez crack that company despite doing little to stand out on a per-inning basis? It helped that he hit well, but more importantly, he threw more of those innings than anyone else—an average of 237 per season, to be precise. The teams that employed Hernandez—the Giants, Expos, and Nationals—weren’t looking for flair. They were buying outs in bulk.

The durability of these DL-averse arms sets them apart from most pitchers. In each of those six seasons, Hernandez finished in the top five in Pitcher Abuse Points, a pitch-count-based metric designed by Baseball Prospectus to assess stress. He’s still going strong, but some of the other names flanking his—Schmidt, Mark Prior, Kerry Wood, Victor Zambrano—broke down not long after appearing near the top of those lists.

On the whole, pitchers are an extremely fragile species. In the 1990s, BP founder Gary Huckabay summed up the steep attrition rate among young arms with the phrase, “There’s no such thing as a pitching prospect.” Most fans understand that a high percentage of pitching prospects don’t pan out, but sometimes it seems as if there’s no such thing as a pitcher, period. A history of staying healthy is no guarantee of continued immunity from the ongoing injury epidemic: a study by Jeff Zimmerman in 2010 determined that over the previous decade, any starter who had pitched at least 120 innings in one season had a 41 percent chance of hitting the DL the following year.

This season, pitcher injuries have been more visible than ever, thanks largely to an uptick in Tommy John surgeries. From 2005-2011, an average of just under 11 Tommy John surgeries were performed through June, according to data collected by BP injury authority Corey Dawkins. This year, the count is already up to 23, with pitchers like Jose Contreras, Felipe Paulino, and Daniel Hudson likely to add to the total in the coming weeks.

With seemingly every day bringing news of new injuries, how is it that certain pitchers have managed to stay healthy year after year? And how might teams be able to find or make more of them?

Some of these well-preserved pitchers have at least one obvious quality in common: less-than-impressive velocity.  According to PITCHf/x data available at Brooks Baseball, the primary fastballs of the top five DL-free pitchers above averaged only 88.2 mph. That’s not a coincidence, according to the American Sports Medicine Institute’s Glenn Fleisig, one of the foremost experts on pitching biomechanics. “All things being equal, the 90-mph fastball is more stress on the elbow and shoulder than the 80-mph fastball,” Fleisig says.

That presents a problem for teams, since velocity often goes hand in hand with success. All else being equal, the harder a pitcher throws, the lower his ERA goes. But that extra speed creates extra stress, and that stress leads to injuries. Thus far, Justin Verlander has combined the durability of a league-average soft-tosser like Livan with the elite fastball and performance of a Cy Young winner, but very few other starters can say the same.

However, it’s never the case that all things between two pitchers are equal aside from velocity. For one thing, every pitcher delivers the ball in his own unique way, and that can mean the difference between a pitcher who breaks down and one who holds up. “If it’s good mechanics versus bad mechanics,” Fleisig says, “that could more than compensate for the difference in ball velocity.”

But what do “good” and “bad” mechanics look like? If it were easy to pass judgment on a player’s mechanics, there would be more major leaguers like Livan. Unfortunately, making sense of mechanics is one of the most difficult tasks facing teams. According to one scouting executive with a major-league club, one of the factors that makes evaluating mechanics so difficult is that there’s no example of optimal mechanics to which each pitcher can be compared. “People say that maybe [Greg] Maddux had perfect mechanics,” says the executive. “But it’s very tough to say that there’s one ideal mechanical delivery, or one ideal arm action.”

Using the precise measurements made possible by motion capturing and high-speed cameras, Fleisig and his colleagues at ASMI have identified a number of mechanical risk factors and designed programs to correct them. He hopes that within 10 years, biomechanical analysis will become automated to the point that data can be collected in games. As ASMI’s methods improve and teams increasingly come to accept them, analysis of mechanics could pay off in better health for pitchers. However, short of sending a pitcher to be analyzed in the laboratory, teams can still learn a lot with the naked eye.

“There are definitely visual indicators that you can see from the stands,” says the executive. “The real good scouts, they’re all over it. It’s something that you can tell by watching if you know what you’re watching for. It’s not 100 percent, but I don’t think anything when you’re dealing with scouting is.”

Faulty mechanics can be fixed—the earlier, the better—but only at considerable risk to a pitcher’s performance. Doug Thorburn, a former biotechnician at the National Pitching Association and the co-author of Arm Action, Arm Path, and the Perfect Pitch, says, “An ideal development path will include mechanical instruction in the early stages, in order to maximize efficiency and minimize risk as the pitcher climbs the minor-league ladder.” By the time a pitcher reaches the majors, Fleisig adds, “It’s more a mentality of, ‘If it ain’t broken, don’t fix it.’”

But mechanics aren’t everything. According to Fleisig, “50 percent of the equation is how much damage you do to your arm, and the other 50 percent is how effectively you repair and recover from your damage.” That means that much more than mechanics goes into the complex calculus of predicting what’s in store for a pitcher, including workload, nutrition, and conditioning. (Bobby Cox once called Derek Lowe’s exercise program the “best workout routine I’ve ever seen.”) And the most important factor of all might be one whose impact on health is still largely beyond our understanding: genetics.

“All of these guys at the major-league level, and maybe most of the guys at the minor-league level, to a certain extent, they won the genetic lottery,” says the executive. “There are things they do that the average person just cannot do. You look at a guy like Livan Hernandez, that’s genetics. He’s not exactly a physical specimen, but he’s just got an arm that works, and he can go out there and pitch and pitch and pitch, and he doesn’t break down, he stays healthy. I’m not going to say that it’s not the product of a lot of hard work, but at the same time, he’s obviously just special.”

Since genetic freaks are few and far between, both Fleisig and the executive emphasize the importance of competent coaching and training staffs. “You want an aggressive athlete,” Fleisig says. “But if the athlete has a good relationship with the coach and the trainer to help read, whether in the training room or on the field, whether he’s had enough today, that player is going to benefit and have a longer endurance.  Likewise, the next day, the player who knows his body and talks to the trainer and says, ‘My arm’s a little more worn out; I need a little more therapy,’ that’s where the people aspect comes into the equation.”

Despite the efforts of Fleisig and others, most of the major advances in pitcher preservation have been made in injury treatment. Injury prediction and prevention have made more modest progress.

“I don’t know that you can say that we’ve made a whole lot of progress,” the executive said. “I think teams can kind of identify the high-risk guys, but at the end of the year, there are going to be a ton of guys you weren’t expecting to break down.”

Given all the uncertainty, it’s not surprising that pitchers like Hernandez and Lowe have continued to draw interest from teams into their mid-to-late 30s. All else being equal—there’s that phrase again—given a choice between an older pitcher with a clean bill of health and a slightly more injury-prone pitcher in his prime, which would most teams choose?

 “The industry will probably say they’re going to go with the older guy, the Livan Hernandez,” says the executive. “You’ve got more to stand behind if you say, ‘We’re going to take the guy with this track record of performance over the last 10 years.’ But when that GM lays his head down on the pillow at night, he’s probably thinking that it’s a coin flip.”

Teams can take several steps to maximize their odds of lucking into the next Livan. They can recruit the best scouts, coaches, and trainers, and monitor their pitchers closely. They can make use of new technologies like PITCHf/x and the motion capturing available at ASMI. But even if they do everything right, they can move the needle only so much.

“Pitchers are going to get hurt,” the executive concluded. “You just hope it’s not your guys at the wrong time.”

Jonah Birenbaum and Rob McQuown provided research assistance for this story.

A version of this story originally appeared on ESPN Insider Insider.

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Given that Doug also writes regularly for BP, it would be really interesting to get him to do an article focusing on the mechanics of the guys listed here.
Doug actually talked about Shields' mechanics a few years ago on site:

BP: One last question. A BP reader recently asked if James Shields' changing mechanics may be due to his regaining velocity and control post-surgerically. Can you address that?

DT: Well, it is likely that the causation arrow is pointing in the other direction, in that his regaining velocity and control post-surgery may be due to changing mechanics, and some of the mechanical alterations may have been necessary due to the surgery. Unfortunately, I am not familiar with the specific mechanical adjustments that he has made since 2002, but I did notice an improvement with his balance and posture in 2007 compared to 2006, which I believe helped with his effectiveness. In general, the easiest way for a pitcher to improve his stuff is to work hard on mechanical efficiency, as well as functional strength and flexibility. Mechanical efficiency can improve real (radar gun) velocity, perceived velocity, command, deception, and the available options for playing the chess match between hitter and pitcher. This is why I have a hard time with scouts that are quick to hand out ceilings and projection, because in most cases they underestimate the ability for a player to hone his skills and improve his talent level beyond raw tools. By definition, player development requires athletes to learn, and the learning curve in baseball is steeper than any other major sport, as evidenced by the minor league system. Learning ability is one of the strongest tools a ballplayer can have, and the motivation to improve through hard work is what separates success from failure for countless athletes. But they can only get so far without quality information and communication, which is where we come in.
Jon Garland was one who never got injured....until he did.
Genetics and pre-professional training/stretching/muscle formation. I think it's probably the same reason some people have tons of allergies and others have none.