As season-ending home runs go, Aaron Boone’s eleventh-inning shot for the Yankees against the Red Sox last October looks pretty unimpressive in retrospect. Watch the video replay once more: a paunchy, goateed pitcher, his cap pulled down low, begins to wind up for what appears to be a practice pitch—hasn’t a batter stepped in already?—and releases the ball from a contorted claw’s grip, right pinkie finger extended, with a prim, abbreviated follow-through, the right foot landing in quick succession after the left, as though in a limp. The miles-per-hour indicator flashes “69” at the top of the screen as the ball floats, then hangs. If you didn’t know better, you might not believe that the Boston pitcher—he’s quietly walking off the field now, as Yankee Stadium erupts with joy—intended to get Boone out, or that he had any business being on the mound in a post-season Game Seven in the first place, much less during extra innings. In fact, though, Tim Wakefield, the pitcher in question, had beaten the Yankees more often than any pitcher all season by doing much the same thing. Sixty-nine m.p.h. is routine for a sophomore in high school; it is on the fast side for a Wakefield delivery.

The Yankees and the Red Sox are engaged in what is often called an arms race. This past off-season, the two teams, already possessing stratospheric payrolls, went about adding more firepower to their rosters. The Sox, most notably, added a couple of hard-throwing All-Star pitchers (New York allowed fewer runs last season), while the Yanks added a couple of All-Star sluggers (Boston scored more). In Fort Myers, on the first Sunday in March, the Yankees arrived at City of Palms Park (Florida’s Fenway) to play the Red Sox in a meaningless early spring-training game that was nonetheless billed by various players and writers as “Game Eight”—the continuation of last fall’s epic series, which seemed merely to have paused for the winter. Before the game, several fans paraded around the grandstand carrying signs taunting Alex Rodriguez, New York’s studly new third baseman (he’d recently posed with his wife for Sports Illustrated’s swimsuit issue), and alluding to the simmering steroids controversy (the Yankees’ new right fielder, Gary Sheffield, was among those called to testify before a grand jury). Obscured by all the commotion was the fact that, in this cold-war buildup, the weakest arm may still make all the difference.

Two miles down the road, at about the same time, a twenty-four-year-old former art student named Charlie Zink was throwing from a practice mound at the Red Sox’ sprawling Player Development Complex, while the rest of the hundred or so minor-leaguers in the Boston organization, spread out over five diamonds, took batting practice and shagged fly balls. Zink was twelve when he first saw Wakefield—then a rookie with the Pittsburgh Pirates—pitching in the National League playoffs, in 1992. Now, although he is capable of throwing standard-issue jock heat, Zink was trying to mimic the Wakefield delivery as well as he could, right down to the apparent lack of exertion and the junior-varsity speed. From a side view, there was nothing at all remarkable about Zink’s pitches, except that occasionally the catcher didn’t catch them. In those instances, the coach who was standing behind the mound tended to exclaim, “That is outstanding!” Zink, who went undrafted as a fast-ball pitcher, is, at the Red Sox’ urging, reinventing himself as a rare specialist: a knuckleballer. With Wakefield, one of only two knuckleball pitchers currently on a major-league roster, and now Zink, the Red Sox are cornering the market on low-grade weaponry. Project Knuckleball is only just beginning its second year, but, according to Baseball Prospectus, a leading baseball-analysis Web site, Zink is already the Red Sox’ top-rated prospect.

The knuckleball—also known as the knuckler, the fingernail ball, the fingertip ball, the flutterball, the floater, the dancer, the bug, the butterfly ball, the moth, the bubble, the ghostball, the horseshoe, the dry spitter, and, curiously, the spinner—has been around, in one form or another, for nearly as long as professional baseball itself, though for much of that time it has been regarded with suspicion. Spinning is precisely what it does not do. In fact, a lack of spin is about the only identifying characteristic of the pitch. There is no right way to hold a knuckleball when throwing it (seams, no seams; two fingers, three), and no predictable flight pattern once it leaves the hand. “Butterflies aren’t bullets,” the longtime knuckleballer Charlie Hough once said. “You can’t aim ’em—you just let ’em go.” The pitch shakes, shimmies, wobbles, drops—it knuckles, as they say. Which is doubly confusing, because the term “knuckleball” is itself a kind of misnomer, a holdover from the pitch’s largely forgotten infancy.

Depending on how you look at it, the first knuckleball was probably thrown in the late nineteenth century, by a bricklayer named Toad Ramsey, or shortly after the turn of the century, by the famous junkball ace Eddie Cicotte. Ramsey, who pitched for Louisville in the old American Association, severed a tendon in his left middle finger (that was his pitching hand), and thereafter adopted a peculiar grip, in which he curled his middle fingertip on the top of the ball, exposing the knuckle. His newfangled pitch probably more closely resembled what is now known as a knuckle curve—a pitch that, despite the name, bears little in-flight resemblance to Wakefield’s floater. (The knuckle curve, thrown today by the Yankees’ Mike Mussina, is released with top-spin, or overspin, and so does not even belong in the flutterball’s extended low-spin family.)

Cicotte, for his part, discovered early in his career that by pressing the knuckles of his middle and index fingers against the ball’s surface, and steadying the ball with his thumb, he could produce a spinless pitch, which would behave erratically and set batters on edge. In 1908, pitching with the Red Sox, he took the nickname Knuckles—by which point others had already begun to figure out that the same flitting effect could be achieved, and with greater control, by simply clamping down on the rawhide with one’s fingernails. The actual use of the knuckles in pushing the ball plateward has essentially been out of style for ninety years.

All told, there have been about seventy pitchers who have entrusted their livelihoods, at one point or another, to the vagaries of the knuckleball (by the count of baseball writer Rob Neyer). Some have preferred to throw a faster, harder-breaking version of the pitch, which arrives in the seventy-to-seventy-five-m.p.h. range, exhibiting only minor turbulence en route to a crash landing. Others have favored a more arcing, directionally indecisive floater—the Pittsburgh Pirates slugger Willie Stargell called it “a butterfly with hiccups”—which takes care to obey interstate speed limits. Neither enterprise is a growth industry. In the past fifty years, the fluttering ranks have dwindled to just a few per generation.

Once comfortably ensconced in the flourishing community of oddball pitches—spitball, palm ball, shine ball, eephus—the knuckleball has fallen victim, in recent decades, to a prejudice against deception and a fear of the unknown. If a kid throwing ninety-five m.p.h. has a bad outing, scouts chalk it up to growing pains; at least he can bring it. If a knuckleballer flounders, it is proof, somehow, that the craft itself—just look at it—is unreliable.