Chargers’ Seau Plays Life at 100 M.P.H. : Pro football: Inspired performance by former Trojan linebacker earns him a niche in San Diego.

Junior Seau is a 6-foot-3, 250-pound linebacker, who is not reluctant to show his emotions, on or off the field.

Whether he is pumping his arms after making a great defensive play or simply helping out an old college friend, Seau does things with gusto.

“You could always tell when he was upset or mad because his voice would get real high,” said Aaron Emanuel, a teammate at USC.

An emotional style has worked for Seau, who, in his third year with the San Diego Chargers, has become one of the best linebackers in the NFL. Last season, Seau was voted to the Pro Bowl, and he is a key to the Chargers’ having the second-best defense in the NFL.

“When I first met Junior before the season, I came away thinking that he was a person who had a strong commitment to winning,” said Bobby Ross, San Diego’s first-year coach. “He was someone who had a tremendous amount of pride in whatever he did.”

Seau may be an NFL success story but he did not begin his career that way.

After being voted first-team All-American as a junior at USC in 1989, Seau left college to pursue an NFL career and was selected in the first round of the 1990 draft by San Diego.

Trouble began for Seau after he signed a five-year, $4.5-million contract. He was expected to be the Chargers’ instant defensive savior, and he pressed to live up to everyone’s expectations for a team that finished 6-10 the season before.

Seau was criticized when frustration, stemming from playing on a losing team, got the best of him in his rookie season. He was ejected for fighting on his second professional play during an exhibition game with the Raiders, whose acquaintance he will renew Sunday at San Diego Jack Murphy Stadium.

“I’m a very emotional person who puts his heart and soul into something,” Seau said. “Things happen from within with me. I am not out there taunting in any way. I just get excited about playing.”

Seau has made the switch from outside linebacker, which he played at USC, to inside with San Diego look easy.

Defensive coordinator Bill Arnsparger uses Seau in almost every way imaginable. On some plays, Seau rushes from the middle and on others he lines up outside. Then, there are times when Seau drops back into pass coverage, making him appear to be playing several positions at once.

“My role changes every week,” Seau said. “I don’t even know what I’m going to be doing going into each game.”

Raider Coach Art Shell says that controlling Seau is the way to defeat San Diego’s defense.

“You know he is going to be at the right place at the right time,” Shell said. “He’s still as active as ever. The guy is all over field going 100 m.p.h.”

In some ways, Seau was destined to be an NFL player.

He was 7 and unable to speak English when his parents moved from Samoa to Oceanside. Tiaina, Junior’s father, for whom he is named, urged his six children to go to college.

It did not take long for Seau, a three-sport standout at Oceanside High, to realize that his best means of doing so would be an athletic scholarship. But he was ineligible for athletics his freshman season at USC because he scored below the NCAA required score of 700 on the Scholastic Aptitude Test.

It was during that first year at USC that Seau decided how badly he wanted to play football.

“The thing I remember about Junior was that he was so mature when he first got to USC,” said Martin Chesley, a former teammate and roommate of Seau at USC. “He was determined to make it. There were times when we would all get together and Junior would be off by himself, doing push-ups. He was just that way.”

Seau was one of the most popular players at USC, but Emanuel remembers upsetting him.

“We had lived next door to each other for a couple of years, but before my senior year we decided to live together to save money,” Emanuel said. “I only lasted there two weeks because I was used to living by myself. But, when I was lagging in getting my stuff out of his place, I found all of (it) in a pile in the middle of the living room. I mean, he put everything there--shirts, shoes, papers--all in a pile because he had someone else moving in.

“We argued for a while, but a couple of days later, he came to me and apologized and said, ‘Let’s put our conflict behind us.’ He was that type of friend.”

It was a difficult time for Seau when he decided to skip his senior year. He was caught between his commitments to the Trojans and his family.

“SC was great to me, but I can’t even measure what it meant for me to be home and to have my mom and dad happy,” said Seau, whose first purchase after signing his San Diego contract was a house for his parents in Oceanside. “If I had to do it all again, I would make the same decision because you only have a short time to play and I felt that it was my time to go.”

When Seau left USC, some believed he and the school were on bad terms. Seau says, however, that he has a great relationship with the school and coaches.

“What people don’t understand is (that Seau’s) whole family dedicated themselves to Junior’s development,” Don Montamble, Seau’s high school basketball coach, told The Times last year. “This is truly a culmination of a loving family getting behind someone and really nurturing him to achieve his goals.”