It's a fact of life that baseball players will get hurt. The season is too long, too grueling for them to remain healthy—teams can't even make it through spring training without seeing players head for the casualty lists; for various reasons, David Robertson, Freddy Garcia, and Nick Swisher have all numbered among the Yankees' injured this March.
Perhaps, then, this is why Joba Chamberlain's trampoline-induced limb-threatening, dislocated-ankle injury rankles so much. Recovering from Tommy John surgery, Chamberlain wasn't supposed to rejoin the Yankees until mid-season, but his rehab had been progressing, a baseball player working his way back from a baseball injury. No, no one can guarantee that Chamberlain would not have gotten hurt during his rehab, but there's a difference between getting hurt because of a baseball-related activity and a non-baseball one that, perhaps, could be avoided.
Then again, there is a question: where does the line get drawn between avoiding unnecessary risks and crushing a baseball player in bubble wrap? I've maintained that as a baseball player, Chamberlain is held to a higher standard when it comes to taking risks, but such a viewpoint has been met with criticism, much of it arguing that if we can't let a baseball player have fun with his kid (indeed, the story of a player being a good father is often too heartwarming to pass up) on a trampoline, what's to say we don't ban them from bike riding or playing catch? Where does common sense end and overprotectiveness begin?
This is not an easy question to answer and to be clear, the degree of injury Chamberlain suffered in relation to the activity pursued is sort of the equivalent of slicing your carotid while shaving. Even those (like myself) who would argue that a trampoline is dangerous for a 240 lb. baseball player, would, in all likelihood, have predicted a sprain or jammed appendage, but not an ankle dislocation that rivals the injuries we've seen in recent seasons to Stephen Drew and Kendrys Morales. Even if you are to agree that a trampoline or any form of gymnastics is too risky for a professional athlete, it's unlikely that you would immediately think of a career-threatening injury.
Still, Yankees fans will remember what happened to Aar0n Boone. The (arguably) most famous basketball injury to happen to a non-basketball player ended up netting the Yankees Alex Rodriguez. Basketball is not usually thought of as an activity with a risk level on par with bungee jumping (it's not; you don't need to sign a liability waiver to do the former), but baseball contracts have been known in the past to include provisions against playing hoops. While not a contact sport, basketball remains hard on the knees and ankles, and while a torn ACL might not end your life, it will clearly affect your ability to pitch on a mound.
One can make the argument that trampolining can be dangerous because of the force put on the knees and ankles when a grown, physically fit man, jumps up and down, but it's not so common an activity that you would expect it to be named as a forbidden activity in a player contract. Indeed, are we to argue that Chamberlain's duty to his team comes before his attempts to be a good father to his kid? There may be some who would put a career before family, but (in an ideal world) not many. We castigate celebrities and professional athletes all the time for poor parenting, then when one tries to be a decent one there's a temptation to castigate again for the choice of activity.
There is no one-size-fits-all line when it comes to off-field activities. Why, after all, should we have considered Mike Mussina's tractors any safer than a basketball game? (Mad Men devotees will understand the reference). Almost all of us engage in some sort of regular physical activity that might be considered dangerous; any athletic activity done improperly can cause injury. Isn't this, after all, why we're always taught to warm up and stretch before running a mile or going full-bore in any sort of game? Had Chamberlain been injured in a skydiving or bungee jumping incident the line between responsible and not would probably seem a little less blurry, but this isn't what Chamberlain (or indeed most any baseball player who injures himself off of the field) did.
Freak injuries will happen. There have been stories told about baseball players throwing their backs out or straining an oblique from a sneeze, or even Joel Zumaya's Guitar Hero escapade. You can't ban baseball players from sneezing or from playing video games, and if you were to ban baseball players from ever spending time with their kids during the season, the talent pool would rival the Atacama Desert. Can a team advise players of off-field activities that might involve unnecessary risks? Sure, but depending on one's definition, the list can get too long, too fast. At any rate, baseball players are not children (okay, so some are technically still adolescents, but there's a giant gap between the maturity level at nine and then at 19), and treating them as such would seem counter-productive.
The line, then, would seem to be drawn at common sense. It's common knowledge that skydiving is risky and video games generally are not; it would likewise seem logical that a baseball player's obligation to do his best to remain healthy and uninjured would keep him from playing football, though not golf. Most people who jump on a trampoline, whether an at-home one or at a gym, don't get hurt, and if they do it's not serious. The risk that someone might get seriously hurt is not unknown, but whether it was a risk that should have been foreseen will vary on who is asked.
So in this case, as in others, the picture might remain blurry. Off the field other players have done worse to their bodies, sometimes in ways that are not legal, let alone ill-advised, and suffered fewer consequences. This is, of course, an inherent unfairness, but as long as humans remain fallible, the unfairness will probably remain. No person, let alone a baseball player, deserves a catastrophic injury when attempting to be a good parent to one's child. Even if you take the viewpoint that Chamberlain committed a baseball crime, the punishment does not fit.