The way Jim Thomas played today in the semifinals of the NCAA basketball tournament surprised almost everyone in the Spectrum except the players on Indiana's bench.

They had no doubts about Jim Thomas, the Hoosiers' "other Thomas," a sophomore who excelled when star guard Isiah Thomas went out of the game against Louisiana State because of foul trouble.

"Jimmy's worked in practice running our offense all year long," said Indiana Coach Bob Knight. "He's been in that position before, because Isiah's been in foul trouble before."

In fact, Isiah Thomas, the consensus all-America point guard, had committed eight fouls more than any teammate going into today's 67-49 victory over Louisiana State.

"The point to be made," said Indiana guard Randy Wittman, a defensive force himself today against Howard Carter, "is that when Jimmy comes in and Isah goes out, nobody gets scared. We know he can sustain our offense."

When Isiah Thomas committed his fourth foul and went to the bench with 16:33 to play, Indiana led, 36-30. When he returned almost 10 minutes later, the Hoosiers led by 16 points and had averaged 1.3 points per possession (most coaches say 1.05 is excellent) with 6-foot-3 Jim Thomas running the offense.

Jim Thomas also got a team-high nine rebounds in his 17 minutes, a throwback to his days as a not highly recruited high-school center in Fort Lauderdale, Fla.

"I was happy for him," said Isiah Thomas. "He just played the same as he always does."

Jim Thomas, a straight-A student in high school and son of a principal tried to take the day in stride. "It comes and goes," he said. "It's nice, but it won't last forever."

Knight removed Jim Thomas from the game after Isiah Thomas and most of the other starters. He, not Isiah, went to the media interview with Knight and another player. And he took Knight's jabs at the press conference and, later, in the locker room.

Jim Thomas sat next to Knight at the postgame interview. "He played well . . . did a great job on defense," Knight said. Then the coach turned toward him and said, "You shouldn't have missed that damn layup."

Later, Knight sought to clear the cramped locker room so his players could shower. The last one to make a move toward undressing was Jim Thomas. Said Knight: "Jim Thomas, will you get your butt in gear and take a shower."

During the season, Jim Thomas has gotten his game in gear by playing against his namesake every day in practice. "I'm just 'the other Thomas' to the people outside the team," he said. "I just happened to be named Thomas."

"It's challenging," he said. "If you want to improve . . . it's a great opportunity to improve yourself. Playing against him and playing against a lot of tough teams early in the year helps you improve confidence-wise. My confidence has grown considerably because now I know what my options are, whether it's offense or defense. So I'm not guessing now about the right thing to do."

Jim Thomas said he has tried to emulate Isiah Thomas in how he takes advantage of an opponent's weak points and how he plays defense. "Especially defense," said Jim.

How Jim Thomas, the only player Knight has had in his 10 years at Indiana who did not come from Indiana, Illinois or Ohio, ended up a Hoosier; is one of those stories of being in the right place at the right time. After his sophomore year of high school, he went to a summer camp in North Carolina because he wanted to play against David Thompson, Monte Towe and Bobby Jones. Also at that camp was Quinn Buckner, the point guard on the 1976 Indiana team that won the national championship.

"Quinn said he'd tell the Indiana people about me," Thomas said. "My senior year, they came down and saw me play in the state tournament in Miami. Then I kept in contact with them. It was all a matter of happenstance."

Another player who got the Hoosiers toing was 6-9 senior Ray Tolbert, benched by Knight in the first half because he was playing so badly.

"He was in the ozone somewhere," Knight said of his only starting senior. "He didn't know what atmosphere. I told him to spread out, breath deeply and relax."

Tolbert started the second half with a dunk following an offensive rebound as the Hoosiers scored 11 straight points and made the outcome obvious.

"The dunk lifted me and my confidence," Tolbert said. "The guys knew I was ready to play. I was trying so hard for what I wasn't doing in the first half.