The Great Unknown of the 2001 World Series sleeps most of the day, warms up throwing at a blank wall, then gobbles hamburgers along with Korean kimchi just before game time. He is so immune to pressure that he once won a game to keep from having to join the military, yet he is so erratic that he suddenly went from being a near major league All-Star to being an optioned-out minor league Sidewinder. An underhander, actually, whose bizarre deliveries and exertions and angles seem to come submarining from somewhere below the dirt and result in some of the nastiest stuff around. Not to mention some of the most frazzled emotions -- among his own Arizona Diamondback teammates.

When Byung-Hyun (in English: “Pop-Up”) Kim closed the D-Backs’ pivotal Game 3 of the NLDS against the Cardinals by walking two batters, stranding five baserunners and retiring the potential winning run in each of the last two innings, Curt Schilling said, “It was the hardest thing I’ve ever watched.” When Kim goes into his spinning, whirling, butt-to-batter, neo-Luis Tiant routine, he’s not actually attempting to screw himself into the mound -- “It’s as if he’s trying to invent a whole new way to pitch,” says Luis Gonzalez. Ultimately, when Kim put the beleaguered Braves out of their misery by facing the minimum number of batters in the final two innings of Arizona’s Game 4 and 5 NLCS victories over Atlanta, Mark Grace summed up his tiny teammate’s presence in practically historical terms: “BK was in command. Concentration, focus, great pitches ... this time. But he keeps us on pins and needles all the time. The little SOB reminds me of Mitch Williams.”

Uh-oh. While the 5'11" (in his dreams), 175-pound (after one of Arizona’s champagne-and-beer celebrations) Kim may be a latter-day Korean incarnation of that nerve-racking pariah of the postseason, a sort of Far Eastern Wild Thing, it is also true that as the Diamondbacks continue to slither their way through this magical fourth season of their existence, the 22-year-old Byung-Hyun, who looks 12 and sometimes acts younger than Danny Almonte, could turn out to be the most important pitcher in the Fall Classic.

Not that the perennially durable duo would require it, but who else can rescue Schilling and Randy Johnson? Not that he couldn’t care less, but who else can the D-Backs match against the Yankees’ nonpareil Mariano Rivera? Kim finished the regular season with 19 saves and a 2.94 ERA, leading all National League closers in lowest opponents’ batting average (.173), strikeouts (113) and innings pitched (98). This despite losing three games and giving up five homers in September. So if Schilling and Johnson start to get bitten themselves late in the gathering mist, manager Bob Brenly has “The Little Unit,” as teammate Mike Morgan calls him, to supply more venom.

Lil’ Kim actually bears lil’ resemblance to his scantily clad, f-bombing, rap-slapper namesake -- though he does tend to expose opposing batters and, according to Greg Swindell, “he now throws back at us all the cusswords we taught him.”

Lucky for them, Arizona GM Joe Garagiola Jr. believes in the sanctity of videotape. “I first saw Kim on tape pitching in the Asian Games against China and it was ridiculous. He literally struck out everybody. (That was the 1998 tournament wherein, if Kim lost, his next assignment would be as a Korean army soldier.) I thought the tape was doctored or something. Then in the World Cup he pitched against all those stars from Cuba, and he did the same thing -- K, K, K everybody.”

Before Garagiola could bring him over, Kim’s family demanded the GM come to Korea to visit. “Everything seemed just okay,” says Joe G. “Then we went to get Kim’s visa at the American embassy. A travelogue was playing on a TV. When it got to the American Southwest -- the Grand Canyon, desert, cactus, cowboys, stagecoaches -- I just pointed at Kim like: ‘That’s us. That’s you.’ He smiled. I knew we were in.”

In May ’99, Kim was 19, the youngest player in the majors, when he debuted for the big club by striking out Mike Piazza to save a game at Shea. By July 2000, he was a certain All-Star, gathering 14 saves in 17 opportunities, twice fanning eight hitters in a row, while racking up a 2.11 ERA. “I’ve never seen a guy with such stuff and such velocity from way down there,” saysformer D-Backs manager Buck Showalter of the submariner’s up-shoot fastballs (ranging from 88 to 93 mph), his flat and sinking sliders and a suffocating change. But when Kim didn’t make the All-Star team, so the story goes, he soothed his sorrows with a wanton weekend at the sauna baths in Los Angeles. “Maybe get Korean massage, eat Korean food, chill out,” he said then.

He cooled off, all right. In his 26 second-half outings he had no saves and an 8.04 ERA -- and was sent down to the Tucson Sidewinders. Despite the falloff, he finished with 111 strikeouts in 70µ innings, a 14.1-K’s-per-nine-innings ratio that left both Johnson and Schilling in the desert dust.

Again this season, after being forced into the closer’s role when Matt Mantei was injured, Kim has been as inconsistent as he is sometimes unhittable. Perhaps the problem is perception -- his own. “I am young so I do what the team asks,” says Kim. “But I am really starter, not closer.”

“The theory is that if you don’t believe you’re a closer, you can’t succeed as a closer,” says Brenly. “I won’t rule out the starting thing -- in the future. But for this team, at this time, we need him to close. Look, the kid hasn’t even scratched the surface of pitching. But I don’t care if he thinks he’s a juggler in the circus. You see this guy just once a game and the unfamiliarity of all his motions and angles makes him near impossible to deal with. He’s our closer and when we get him to throw strikes, he’s as good as anybody.”

As in two crunch-time performances against the Cardinals, when Kim got Jim Edmonds to fly out in the eighth and Mark McGwire to ground into a game-ending double play. As in Game 4 against the Braves, when Kim entered with the bases loaded and nobody out. “He chainsawed Javy [Lopez] on the first pitch, broke his bat, double play. Got Marcus Giles on a liner, inning over,” recalls Brenly. “This kid is a much better competitor than people think. He wants to be the guy we look to.”

Mostly because of his age and the language barrier -- Kim’s first interpreter was a bad actor who would translate Kim’s obviously thoughtful answers with “he said no” -- the older D-Backs look at their exotic teammate as they would a Disney character who relates more to their kids running around the clubhouse than to themselves. But just as they have gotten used to his strange customs -- his pre- and postgame hour under the stands throwing balls from a bag against a wall (thump, thump), the Tupperware full of Korean delicacies, his flashy, neon equipment (when he debuted a garish orange glove in New York, the Mets demanded successfully that it be outlawed), his sign for a timeout (he’ll cross his arms in front of his body as if warding off vampires) -- the Far Easterner in the New West unveils a new changeup. This year Kim, still struggling with English, nixed any interpreter, feeling such an arrangement set him apart from teammates. Brenly applauded the move as a step toward “maturing.”

“But he’ll still sleep anywhere: clubhouse, floor, dugout, bullpen,” says Gonzalez. “Kim loves our bus. He’ll curl up by a window and it’s like he’s in one of those baby seats. He feels the rumble of the tires and he’s out. Two or three times we’ve gotten off the bus, everybody’s quiet, and we tell the driver just go ahead, he’ll find his way back.”

Fortunately for the Snakes, on the way to their improbable World Series, Kim always has. And now he really is juggling in the biggest circus of all.

This article appears in the November 12 issue of ESPN The Magazine.