Just another innocuous training-camp play: Chris Culliver, running downfield under punt coverage, feels his knee give way. He collapses onto the turf, and, in addition to physical pain, dreads the worst. Not only has his leg collapsed, but what about his practice session, his season, his career, his entire life-path? Perhaps initially inconsolable, he soon turns his thoughts to rehab.

49er's draft room, 2012, the first round: Trent Baalke and his brain trust have targeted several possible players to take with their first pick. They have done due diligence, have scouted intensively, planned thoroughly, have medically and mentally assessed each prospect. Tick tock, tick tock. Their pick arrives. They do not trade it; instead, they select wide receiver A.J. Jenkins. Beyond Baalke's supposed back-pocket envelope, the team has high hopes for Jenkins, and so does the fan base. Maybe the speedster can add immediate pizzazz to the offense. However, more than a year later, with the 49ers desperate for wideout help, Jenkins still struggles to contribute. Eventually, the 49ers trade him.

Of course, it's still too early to tell, and mostly we hope that both players can overcome their troubles and have successful careers. But, beyond the personal travails of each individual, both these situations edge toward miniature versions of what Nassim Nicholas Taleb calls, in his bestselling book of the same title, "Black Swan" events. (Actually-existing black swans were reckoned a physical impossibility in the Western world until a Dutch explorer "discovered" in 1697 some of those graceful water-gliders on an Australian pond.) Black Swan events arrive unbidden, unforeseen, and seemingly out of nowhere. Randomness makes mincemeat of what sports announcer Vin Scully frequently calls "the best-laid plans of mice and men," plans that, more often than we would like to think, do often turn awry.

However, we deal with football here, not philosophy or the Los Angeles Dodgers. So let us use another term to describe a similar, but more down-to-earth, phenomenon, one used by the original 49ers to refer to a dud gold mine or dry well: buzzard's luck. One may expect, anticipate, and even somewhat prepare for run-of-the-mill bad luck. But buzzard's luck is worse.

For instance, one might write off one of Kyle Williams's muff/fumbles in the NFC Championship game against the New York Giants a couple years back as lack of focus or a lapse in ball security. But with two miscues, both at critical junctures in the game, in addition to a similar mistake in college, we now lurch somewhat beyond the bog of blame, and closer to the realm of sheer buzzard's luck. The following year, Williams sustains a season-ending injury. One more setback, and the young man may begin to see those blue carrion-bird shadows commence to circle.

"The blues don't care who's got ‘em." "Wasn't for bad luck, I'd have no luck at all." "I asked for water, and she gave me gasoline." In other words, bad luck enough that she didn't give you the water. That she gave you gasoline instead, that she even had it on hand, that's lowdown gutbucket buzzard's luck, even if you may have deserved it, even if you refuse to use ill luck as an excuse.

Branch Rickey once dubbed luck "the residue of design," but buzzard's luck can disrupt, precisely, the keenest designs. Some teams seem permanently stuck in a slew of it: the Chicago Cubs. The 49ers before Walsh occasionally blurred the boundary between buzzard's luck and just plain bad. Even good teams sometimes flirt with it. Take the New England Patriots, one of the most consistently successful teams of the last several seasons. Their defense, thanks to attrition and a run of iffy draft choices a few years back, declined. But the Pats avoided complete buzzard's luck, fortuitously hit on some draft picks, and their defense subsequently improved. Likewise the current San Francisco Giants, winners of a couple World Series, now may perch on the precipice of vulnerability to buzzard's luck (some would say they're already in the middle of it).

Of course, bad luck can womp both ways, can strike foes and friends alike. For instance, during this summer past, two of the 49ers' chief rivals for NFC supremacy, the Green Bay Packers and the Seattle Seahawks, have lost important players to injury, respectively, an offensive tackle (Bryan Bulaga) and a multi-threat offensive player (Percy Harvin). Further deterioration at these positions to the point of buzzard luck, in addition to the individual traumas to the young men involved, would seriously diminish each team's prospects. Every NFL team expects injuries, but most hope to avoid decimation at a single position. Currently, the 49ers have attempted to shore their wide-receiver core against further ruin through sheer numbers.

Positive Swans, as well as negative ones, can swoop in unexpectedly. Perhaps a defensive back from the back end of the Niners' roster may yet emerge as a shutdown corner. Or maybe Mr. Baldwin, acquired for Jenkins himself, against all odds will make large strides. (Given his NFL output so far, such an outlier might, indeed, qualify as a Black Swan event.)

Also, invariably, some team from seemingly out of bottom-of-the-league oblivion will ascend to playoff contention. And, when they do, we will acknowledge their front-office acumen, note statistical improvements, and applaud their superior players. All to the good; we generally appreciate fresh faces, and feel that excellence should merit rewards. And, yet, on the long list of reasons why they've succeeded, one element may languish near the bottom: that simple serendipity enabled by the lack of bad luck.

So, as we embark on yet another NFL season, maybe faithful fans might just as well stay positive and, rather than succumb to bouts of teeth-grinding, regard the inevitable random bounces and chance outcomes with a more resigned, even bemused, stoicism. Hell, you can't control fate anyway; as one of Vince Lombardi's ancestors once said about misfortune, you can only hope to endure it. Those black swans will continue to slice through still water. And those blue buzzards, tireless in their hunger, never rest for long.