Jim Ostertag remembers watching his only son playing high school ball. An errant shot would glance off the rim, and Jim would grimace at the sight of his 6-foot-10, hat rack-thin boy standing flat-footed and grabbing the loose ball.

"It bugged me," said Jim. "When he didn't jump for a rebound, I'd get on him. You know what he'd say? `But daddy, I don't have to jump.' "What makes Greg Ostertag jump?

Throughout his mercurial career, many have tried to prod Ostertag to jump, literally and figuratively. But lighting a fire under the enigmatic big man has proved a tall order.

Since signing his name to that eye-popping, six-year, $39-million contract extension last September, a giant question mark has hung over the head of the Jazz's third-year center: Is he a franchise cornerstone or yet another undeserving millionaire with an overactive pituitary gland?

He stands 7-feet 2 inches tall. All arms, legs, feet and goofy grin. He sports a tattoo of a dunking Fred Flintstone on his calf (tlypifying his yabba-dabba-do approach to the game as well as life) and has the wingspan of a condor.

It's this body by Hanna-Barbera that has caused more than one basketball savant to refer to the Big O as the Big X in the Jazz's quest to return to the NBA Finals.

So far, Ostertag has been an expensive NBA tease: When you think he's on the cusp of becoming a dominating defensive presence, he turns into the second coming of Walter Palmer.

One minute, he's skillfully swatting away the shot of David Robinson. The next, he's heaving an air ball from the free-throw line. He's either ripping down a rebound, running the court and filling the lane for a slam dunk, or he's standing like a maypole while Tim Duncan maneuvers around him.

His heart has been questioned publicly, yet Ostertag has had strong games against some of the top big men in the league. Lacking, however, have been consistently strong games.

Now awaiting him in the next round is his basketball arch-rival (if an oversized, goofy-looking kid from Texas can actually have an arch-rival) - the Los Angeles Lakers' Man of Hype - Shaquille O'Neal.

While it may be of little consolation to Jazz fans flummoxed by the up-and-down fortunes of Ostertag, they may take comfort in knowing that historically, "Tag" usually saves his best play for when it counts most.

You can look it up. In 1991, as a high school senior, he led Duncanville High to its only state championship, no small feat in a state where 256 schools were vying for the 5A crown.

The previous year, the Panthers had lost in the first round. It was a painful experience for Ostertag, who vowed that he would lead his school to a championship. Though he guided his team to a 37-2 record as a senior, it wasn't until the playoffs that he was focused and took control. "He became a different player," said his coach, Phil McNeely, whom Ostertag credits with helping develop his game. "It was important to him."

By the time McNeely removed him from the championship game, with two minutes remaining and Duncanville enjoying a comfortable lead, Ostertag had 35 points, three more than San Antonio High. And the school had its championship.

"In those last five or six games, Greg took over," Jim remembered. "I'll never forget that. Maybe he woke up."

To this day, Utah's Sleeping Giant acknowledges it was his best performance as a basketball player. "I was on a mission," Ostertag said. "I told myself, `This is your final chance.' It wasn't all me, but I took it upon myself to win it."

If only Jazz coach Jerry Sloan could kindle that competitive fire for the remainder of the playoffs and beyond.

AS DOCUMENTED, Ostertag has shown flashes of brilliance in his three NBA seasons. He was the darling of Utah's 1997 remarkable playoff run. Everybody remembers Game 6 of the Western Conference Finals for John Stockton's 3-pointer that sent Utah to the NBA Finals. Few remember that in that same game, Ostertag was perfect from the floor and free-throw line, scoring 16 points. He also grabbed 14 rebounds and had three blocked shots.

In Game 5 of the NBA Finals against the Chicago Bulls, he scored 13 and recorded a career-high 15 rebounds. Most recently, in Game 5 this season against Houston, he blocked seven shots. He had nine rebounds and three blocks in Game 4 on Sunday against San Antonio.

Such stellar moments have been few and far between for Ostertag this season, however. Many feel he got complacent after inking that mega-contract (this year he's making $700,000, from the pact he signed as a rookie).

But McNeely, who remains close friends with his former player, says money doesn't motivate him.

So what does? "If I knew that, I'd be a genius," McNeely said. "It's just his personality. He needs to be more hard-nosed. I think he realizes now he needs to work. I tried to get him to take it as serious as I did. Sometimes I wanted him to be meaner on the court. It's pretty hard to change someone's personality."

More telling is what Ostertag uses as motivation.

"I have no idea," answers Ostertag. "That's something I need to find an answer to."

He shares one hint. "I take pride in my shot-blocking," he said. "I want to be in the top five all-time in shot-blocking when I leave the NBA."

But to do that, he must improve upon his forgettable performance in 1997-98. The preseason began with him incurring the wrath of teammate Karl Malone for showing up to training camp out of shape.

Then came the infamous O'Neal slap hours before the season opener. That was followed by a horrendous slump that cost him his spot in the starting lineup. In December, he and Sloan engaged in a shouting match during a game at Washington, which saw Ostertag banished to the locker room.

His next travail was a stress fracture in his leg, causing him to miss 17 games. Then Malone blasted him on national television, blaming the injury on lack of off-season conditioning.

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EGARDING HIS BATTLES with Malone, O'Neal and Sloan, Ostertag refuses comment. Rather, he has focusd on making amends during the postseason. However, those volatile incidents have bothered Ostertag this season and have contributed to his struggles, according to both his dad and his ex-coach.

One piece of tangible evidence reflecting his decline this season is in his free-throw percentage, which has dipped to Shaq-esque levels. A career 67 percent shooter from the line going into the season, Ostertag shot just 48 percent this season and is only 8 of 20 in the playoffs.

Ostertag readily admits he has struggled to meet lofty expectations. "I've never lived up to my potential. Since I went to Kansas, my game went south. I don't know why. I went to a great school, played for a great coach. If I had to do it over, I would have prepared better for college and pro ball. I would have worked on my game and my body more."

As a youngster, his height was, simultaneously, a blessing and a curse. On the one hand, the game gave him confidence and an identity during his formative years. "He didn't like being tall," said McNeely. "Basketball helped him see that being tall can be a positive."

Yet the game was too simple. He was rarely challenged and didn't see the need to work hard. "It came so easy for me," he said. "I was so much bigger than everybody else. I'd get four or five offensive rebounds on one play."

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T WAS IN rural hometown of Duncanville (pop: 40,000), located 10 miles south of Dallas, that Ostertag became infatuated with the game. Infatuated, yes, but never obsessed by it.

In fact, basketball won't likely be part of Ostertag's life after leaving the NBA. When he retires, he wants to move to Texas with his wife, Heidi, and his two children, Cody and Bailey, and run a ranch. He'd rather be hunting and fishing than coaching or scouting.

McNeely agrees. "With some kids, basketball is a passion. He likes his time away from it, too. He's a big-hearted, good kid. If he wants to make up his mind to do something, he'll do it. He's not going to ruffle anybody's feathers. If it's not important to him, he'll go fishing. If he weren't 7-2, he'd be selling hunting gear or something."

"He's in his own little world," says Jim Ostertag. "He's a happy-go-lucky kid. If you can't have fun being alive, why be alive? That's how he looks at it. He doesn't worry about small stuff."

While football is king in Duncanville, as in the rest of Texas, basketball is no court jester. Among some hometown residents, Ostertag enjoys near-royalty status. The championship banner that hangs on the wall of the basketball gym at Duncanville High serves as a reminder of Ostertag's contribution to the community. In McNeely's office, the state championship trophy is prominently displayed, as well as photos of his former star.

A few miles away, a Jazz banner dwarfs an American flag that hangs outside the Duncanville home where Ostertag grew up. During this past regular season, Jim and Jean Ostertag watched their son play on TV, thanks to a backyard satellite dish. According to their daughter Amy, mom and dad "live and die with each shot."

THE OSTERTAGS ARE a tight-knit clan. For four years, Jim and Jean would drive 525 miles on weekends to Lawrence to watch Greg play in college. Like his son, Jim is a laid-back type. Jean, a securities trader for a Dallas brokerage, has been and remains the driving force of the family.

"Mom gets on him (Greg) when they talk on the phone," said Amy, 23, who works as a secretary for a Duncanville law firm. "Ask (Greg) the one person who he's most afraid of. It's his mom."

Ostertag agrees. "I feared her growing up," he explained. "She's an enforcer."

But Momma Ostertag is also her son's biggest fan. "In high school, if it was a close game, she'd be so nervous, she'd go help with the concessions," Greg recalls. "Now, after games, she wants to know my stats. We talk about plays."

Jim Ostertag, who's 6-7, is a registered nurse who moonlights as a baseball umpire. He coached his son in all sports, emphasizing baseball, which is still Greg's favorite sport.

Greg was always the biggest kid in his class, including the teachers, and also one of the youngest. Batters who played against Jim's Little League teams had to stare at a 6-foot-8 13-year-old pitcher on the mound, 55 feet away. "I wanted him to be a baseball player so bad," said Jim.

"When (Greg) hit 6-9, I realized baseball wasn't going to be his sport. I always told him, `If you can block shots and rebound, you can play in the NBA.' That's his forte more than anything. I worked a lot with him when he was young. I was harder on him than on the other kids that I coached."

For McNeely, the fact Ostertag is even playing in the NBA is quite remarkable. "Who would have thought he'd be playing against Michael Jordan?" he said. "Who would have dreamed it?"

Jim Ostertag realizes his son has been in and out of the doghouse this year. "I don't get involved in that stuff," Jim said prior to the start of the playoffs. "He's an adult now. The Shaq thing was blown out of proportion. It's the same two things the national announcers say every game, about Shaq and Karl. It upset me at first. But that's between Greg and them. Did he struggle this year? Yeah. But during the playoffs, you wait."

So far, the Jazz and their legion of fans are doing just that - waiting for their question mark to become an exclamation point.