“Do you know my dad?” Keith Costas, 3 at the time, asked his nursery-school teacher.

“Well,” she replied, “I’ve seen him on TV, but I’ve never actually met him.”

“Trust me,” Keith said. “He’s a goofball.”

Sure is. This is the fellow who, early in the 1986 baseball season, told Minnesota Twins outfielder Kirby Pucket that if he was batting .350 at the time Costas’s wife delivered, Costas would name the baby in his honor. In May, Puckett was hitting .372–and Keith Michael Kirby Costas was born. This also is the guy who called elevator races on David Letterman, hired Chubby Checker to sing at his wedding and announced on an NBC promo that he once played for the Toledo Mud Hens and then was pitching coach for the New York Mets in 1962 (when he was 10).

But Costas knows when to put a lid on it. When news of Roger Maris’s death came over the wire minutes before a football telecast was going off the air in 1985, Costas offered a tribute so moving the family asked for a tape. As a link to the chords of childhood, in his wallet he carries baseball cards of Mickey Mantle and the ‘61 Yankees. Despite being in Manhattan so often, he continues to live in St. Louis because he thinks it the best place to raise his children; he met his wife, a schoolteacher, there.

His fusion of reverence and irreverence has made the 40-year-old Costas the most admired sportscaster in America. He combines the intelligence (and stature) of Cavett, the quickness of Carson and the sensibility of the Little Rascals. Those gifts have been displayed not only in the venues of sport, but since 1988 in a wee-hour interview show, “Later,” which has become a cult favorite for the post-Letterman crowd. On “Later,” Costas does 30 minutes of contemplative one-on-one with guests ranging from Elie Wiesel to Dennis Hopper to Mr. T. Past glories, though, pale before the possibilities of his next assignment.

Next week Costas goes big-time prime time in what will be the defining moment of his career. He’ll be Anchor to the World, as the studio host of NBC’s coverage of the Summer Olympics. For 80 hours, over 17 days, Costas will guide a total of 200 million viewers from ringside to poolside, from marathon to decathlon-always at the ready, he hopes, with an anecdote, antidote or grace note. On the first day of competition alone, he’ll do a herculean 11 hours. NBC, which shelled out $401 million for the rights, has a lot riding on him. The host of the Games can arouse an audience or anesthetize it; in the annals of Olympic broadcasting, both have a rich tradition.

Under the stadium lights, on a cumulus-filled Monday in Portland, Ore., Bob Costas is in heaven. It’s early June, but the Olympics are far from his thoughts. Tonight is for baseball, even if it’s the Triple-A Beaverson Count the Attendance Yourself Night (winner: 843). As usual, he’s sporting the GQ look, except for a Mud Hens cap. Costas may be in town to cover the NBA finals, but baseball is his love. He does an 80-minute interview for an upcoming cable documentary on baseball movies, then stops by to do an inning in the KFXX radio booth. On the way out, he’s still talking baseball. “Just tell me why they can’t make a great film about Babe Ruth.”

The gravity of baseball has pulled on Costas since he was a boy. It was a bond with his father. John Costas died at 42 of a coronary, as Bob was finishing high school. “I remember every game we went to at Yankee Stadium-the drive there, what he was wearing, what we talked about,” Costas says. “Baseball is Bob’s absolute truest emotion, what connect’s him,” says Dick Ebersol, president of NBC sports. “As much as he doesn’t like me calling him ‘young Bob,’ a part of him wants to be thought of that way, as a boy of wonder.”

For young Costas, baseball, too, was about drama and history and the imagination. Growing up on Long Island, Costas would savor every word of Mel Allen and Red Barber. Sometimes he’d go outside to the Ford Galaxie, turn on the AM and pull in Ernie Harwell from Detroit, Bob Prince from Pittsburgh, Jack Buck from St. Louis. During time in Los Angeles, he learned the cadences of Vin Scully; today he’ll break into a B + rendition of Scully at the mere mention of the Dodgers. “Their voices were as much a part of the game as the players,” he recalls. “These were my heroes just like Mantle.”

By age 12, Costas figured out he wouldn’t be succeeding the Mick. Those who can’t hit, pitch. Those who can’t pitch, hit. Those who can do neither, go to communications school. At Syracuse, where such lights as Marv Albert and Ted Koppel began, Costas worked campus radio and got a local broadcasting job. During his senior year, he left school to join KMOX in St. Louis, the sportsradio flagship ofthe Midwest. “I would have been more than willing to pay my dues,” he once said, " but nobody ever made me."

Yes, well, unrelenting ambition didn’t hurt. In Syracuse, Costas got the announcer’s job for minor-league hockey despite never having worked the sport; he submitted basketball tapes instead. “I don’t happen to have any hockey available right now,” he told them. At KMOX, he was asked to do playby-play for the St. Louis Spirits, even though he’d done only a dozen college games. His edge: he doctored his audition tape, taking 10 rousing sequences from his two-hour call of Syracuse vs. Rutgers. Then, to sound older, he re-recorded the sequences with the treble down and the bass up.

Given his affinity for radio, he might have spent his career at KMOX. But part-time regional announcing for CBS beginning in 1976 gave Costas a taste of network television. And four years later, NBC, looking for young talent, offered him the main course. His flawless delivery, mastery of mechanics and mainframe memory all made him a prize at 27. Costas covered football and basketball for a few years, until he got his wish: in 1983, he was teamed with Tony Kubek on the backup baseball Game of the Week. " I showed some whimsy, but mostly I was overwhelmed," is Costas’s self-critique. “I was young, looked even younger, and my approach was rigid.”

Costas the Wit emerged gradually. He spent time with his boss Don Ohlmeyer, who found that Costas made him laugh-on the golf course or at lunch. “Do that on the air,” Ohlmeyer advised him. Somebody should have informed Kubek. One afternoon at Wrigley Field, Costas spotted a banner in the bleachers equating Cubs management with the Three Stooges. The TV camera dutifully showed it. “So, Tony, who’s your favorite Stooge?” Costas inquired of his partner.

“What?” Kubek asked. “OK, Curly. He looked the best.” As play on the field continued, Costas kept at it. “Mine is Shemp,” Costas said. “Very underrated. Sort of a utility Stooge. He’d come off the bench to provide immediate idiot relief when some other Stooge went on the DL after being hit in the head by Moe with a pipe.”

Costas’s official debut in the land of network irony came on Letterman in 1982 (when they couldn’t locate Albert). Since the fabled elevator races, Costas has gone on to star in Viewer Mail, Swivel Chair Relays and calling the delivery of a baby at Lenox Hill Hospital. " I made that weasel," growls Letterman, “and I can break him.”

Not likely, Dave. Bob’s bigger than you now. Yet Costas must match expectations–as he was able to on the late-night wrap-up show from Seoul in 1988. For two decades, Jim McKay of ABC was the Olympics model. Last winter Tim McCarver and Paula Zahn of CBS were so uninspired they could have been hosting a podiatrists’ convention. Costas understands the stakes. He left for Spain a month early, carrying briefing books befitting a presidential candidate; already he’s sleeping days and working nights to get ready. “If NBC gives me the space and opportunity,” Costas says, " I’ll be more than a master of ceremonies. I’ll offer a voice that is truly mine. If not, it will be, monumentally disappointing to me."

So, too, if he gets lousy reviews. Costas can’t stand to be misrepresented-especially if it paints him as a " TV guy," a blowdried shill who can’t even spell moron. Friends say he’s still burned at a 1989 Sports Illustrated piece that accused him of “slinging flutterball wisecracks” rather than tough questions. “I’m not sensitive to being told I called a bad game,” Costas says. “But when an article like that just gets things wrong, why should I accept it? What bothers me more is that people think it follows me down the corridors of time, that I’m some angry young man. I’m not.”

By any reckoning, Costas has a dream job–in Barcelona and beyond. His broadcasting universe keeps expanding so much so that he’s continually denying rumors that he’s in line to succeed Bryant Gumbel on “Today.” (He wouldn’t want it, he says, unless they tape the night before, in which case it wouldn’t be “Today.”) The industry respects him, his public adores him, he happens to make over $1 million a year. So why is this man not wholly satisfied, the Olympics notwithstanding?

He’s always been driven, as if a lack of momentum would suffocate him. Now he wants more. At NBC, that might include a prime-time interview modeled after Barbara Walters’s specials or a sports version of " Nightline." But it largely means a return to the diamond of storytelling, and the chance again to be Red or Mel. NBC lost baseball to CBS in 1988. CBS’s deal is up at the end of 1993. So is Costas’s contract. Graciously but insistently, he hasn’t let NBC forget the coincidence.

“I’m at the point in my career where I want my assignments to reflect even better my personal stamp,” he says. “You try to exist in the peculiar world of network television and still keep your soul.” Not a goofball’s notion at all.

NBC’s mainstay in Spain for 80 hours. Will we long for Jim McKay?

Host of “Later,” the show after Letterman. He’s on that, too.

Host of “Coast-to-Coast,” radio sports chat. GQ look not needed.