Last Saturday, a quarterback scarcely recognised beyond his inner circle until recently sculpted a performance so scary-good that none like it has ever transpired in the nearly century-old National Football League.
Colin Kaepernick is a second-year player whose mid-season promotion to starter in San Francisco gave rise to considerable second-guessing. The 49ers were winning with Alex Smith at the wheel, went the debate, so why mess with success?
Jim Harbaugh, the coach, came to the realisation that the position was mutating, and he thought Kaepernick could get the Niners out in front of a trend that favours quarterbacks who can advance the ball by using the majority of their limbs.
Kaepernick looks the part. To peer directly into his eyes, you probably must arch your neck. He is 6ft 5ins, a desirable height for throwing over linemen.
To follow him dashing up and down the field, your head must be on a swivel. He has been clocked at 4.53 seconds in the 40-yard sprint, which, by quarterback standards, is approaching the speed of sound.
Attach a powerful, accurate right arm to this body, and you might have the prototype for a contemporary quarterback.
In a splashy introduction to the play-offs, Kaepernick established a new benchmark for rushing quarterbacks, with an unprecedented 181 yards (and two touchdowns) in a mere 16 carries. His 17 completions accounted for two more touchdowns as San Francisco gutted the Green Bay Packers 45-31.
The new-age quarterback comes in various shapes and sizes. Russell Wilson of the Seattle Seahawks stands a half-foot shorter, but he covers ground only a blink of an eye slower than Kaepernick, at 4.55 seconds in the 40.
On Sunday, Wilson, whose passes seem guided by radar, gobbled up 60 yards on seven runs in an offensive-extravaganza loss to the Atlanta Falcons. Among quarterbacks this season, he ranked third in rushing, just ahead of Kaepernick.
There is a sobering side to this revolution. The year's foremost ball-carrier lined up behind centre watched both games - assuming he watched at all - with his right knee wrapped and propped up, facing months of rehabilitation.
Robert Griffin III of Washington is tall, strong-winged and so fast that he might someday have cleared hurdles in the Olympics. But whether to deploy such players in diverse fashion falls in a grey area ... because they can wind up black and blue. Griffin was pummelled by tacklers - and abused by his head coach - to the point where he needed reconstructive knee surgery.
(The No 2 quarterback rusher, by the way, was Cameron Newton of the Carolina Panthers, which means the dashing foursome have completed an aggregate six seasons.)
You often hear how maddening it must be for a defensive coordinator to scheme against RGIII, Newton, Kaepernick and Wilson. But pity the guy pulling the offensive levers. Does he deploy these quarterbacks to maximise their skills, or rein them in to save each from injury? Tough call.
A head coach might express a willingness to lop off a few years of his career to direct a player of such multiple talents. Hook him up to a lie-detector test, however, and you might find that he prefers an old-school drop-back passer to spare himself from adopting a high risk-reward strategy.
Case in point: Michael Vick, from whom the new breed directly descended. At the height of his career, Vick was all the rage: the fleet, elusive threat that others wished to clone.
Now look. The book on Vick is that his tendency to run headlong into injuries is not worth the trouble. If you take a chance on these types, you must invest in a backup of first-string capability.
There is no universally accepted way to use these folks. Griffin, Newton and Kaepernick, to varying degrees, keep the ball — especially in the voguish read-and-react, whereby the quarterback rolls out and either unloads or retains it, depending on how he reads the defence.
In Seattle, by contrast, Wilson rarely takes off with ball tucked under arm, except on scrambles when a pass play breaks down.
An architect of the read-and-react was a college coach, Chip Kelly, whose methods were long considered too avant-garde for the NFL. Exposing the quarterback on run plays, as he has for years at the University of Oregon, was regarded as a recipe for disaster in the professional ranks.
Philadelphia have just announced Kelly as their new head coach. Although he is reportedly willing to scale back the read-and-react with the Eagles, even if Vick remains on-board, the hiring signals a further departure from predominantly pass-only quarterbacks in the league.
Colin Kaepernick, what hast thou wrought?