Tim Witherspoon says Larry Holmes' only weapon is a left jab and that once he gets past the jab, he's going to make Holmes pay for the week of insults the heavyweight champion has heaped upon him here. Pardon me while I get up to leave, this is where I came in. A decade of fools said Ali had only the jab. Right. He needed nothing else, and neither does Holmes.

Witherspoon says he will rush inside against Holmes, rendering the jab useless. Once inside, Witherspoon says he will bang away at Holmes' body. This is good strategy. The jab is effective only at arm's length where Holmes can get leverage behind it. Then it lands heavily. But if Witherspoon, a former all-Philadelphia tight end, forces his way in close, Holmes' jab has no room to work.

"Tim's strength will overpower Holmes' experience and knowledge," said Slim Robinson, the old middleweight fighter now Witherspoon's trainer. "The challenger has to go take the title from the champion. So we'll rush him, make him move, see how much those 33-year-old legs can move. We'll smother the jab. If we can control Holmes' left hand, we will control the fight."

Forty-two others with the same idea--Holmes is an uncomplicated opponent--have failed in 42 tries. Now comes Tim Witherspoon, 25, with only 15 fights, saying he can do it. Not only will he survive the rat-a-tat-tat of Holmes' jab, he knows what he'll say to the poor, suffering ex-champ afterward.

"I'll say, 'Larry, I respect you, you were a good champion, the greatest, but now I'm the champ,' " Witherspoon said.

Holmes is so good that all rivals shrink in his presence. Witherspoon is undefeated, his last victory a decision over Renaldo Snipes, who six months earlier had knocked Holmes down before losing in 11 rounds. Of Witherspoon's 15 victories, 11 are knockouts.

"Either hand," Robinson said. "The first three knockouts were the left hook. The next three were the right."

But is a kid with 15 fights ready for a great champion?

"You hear of Pete Rademacher?" Robinson said. "His first fight was for the championship, and he had Floyd Patterson down. Muhammad Ali was a 7-to-1 underdog against Sonny Liston. The favorite got beat. Those odds are similar to this fight. Then something happened to Ali himself--he lost to a guy with only eight fights, Leon Spinks.

"Snipes was 15-0, he had Holmes on the deck in the seventh round and if he'd known how to put him away, he'd be the heavyweight champion. Then Snipes ran from Timmy for six rounds. The referee had to tell Snipes to stand and fight."

Off the Snipes victory, Witherspoon rose to No. 3 in the World Boxing Council ratings of contenders, behind Greg Page and Snipes. Now it is his turn against Holmes, who is taking him so seriously that he has stepped off the curb to demonstrate a certain distaste.

At 33 after 10 years' work and 14 defenses of the championship he won on June 9, 1978, Holmes could be excused for getting bored. Only Joe Louis ever held the championship longer. Holmes also knows boredom precedes defeat. "Witherspoon can tear my head off with one punch," he said. So Holmes, in the crudest Ali-esque fashion, has staged confrontations with Witherspoon.

"He's being followed everywhere by the '60 Minutes' TV cameras," Witherspoon said. "For the cameras, he hollered at me in the casino hallway. 'There goes that dummy I'm going to knock out,' he hollered. So I went towards him and said, 'Make sure you have a stretcher there Friday night.'

"Holmes said some profanity. He said he'd put me and my family back in the soup line, which is where we've never been. My mother is an EKG technician and my father has driven a truck for 25 years.

"I told Holmes, 'We can fight right here.' He turned his head. He just was trying to see if I'd take it. If I didn't stand up to him, he'd know he had me. He threw a towel in my face, too. I said, 'Are you for real?' When he saw I was serious, he was scared."

For $250,000, or about 100 times his first payday, Witherspoon now fights a man who has been the champion longer than the kid has been a pro. Although on football scholarship, Witherspoon says he quit Lincoln (Mo.) University after a semester to work as a "glorified flunky" at Pennsylvania Hospital back home.

"They treated me like a guinea pig at the hospital," he said. So at 20 he returned to the game he tried first as an 8-year-old who had watched films of Sugar Ray Robinson and Muhammad Ali.

"I'd play around with my friends, but it got serious after a while," Witherspoon said. "Good thing I watched those films and played football, or else I'd be down there robbing stores."

His biggest achievement is the victory over Snipes a year ago. He hasn't fought since because an ear infection put off one bout and a broken jaw another. The Snipes' victory is hard to evaluate because Snipes fought curiously, choosing to run instead of stand and slug as had been his custom.

"He ran," Witherspoon said, "because I laid a hard shot into him. I said to him, 'This is what it's going to be like the rest of the fight.' He took off running. I guess he thought I was crazy."

Will Witherspoon talk to Holmes that way?

"If I have to apply it, I have to," he said, trying to sound tough. Tonight's Program

World Boxing Council heavyweight champion Larry Holmes (213 pounds) vs. Tim Witherspoon (219 1/2).

World Boxing Association heavyweight champion Michael Dokes (223) vs. former champion Mike Weaver (218 1/2).

Greg Page vs. Renaldo Snipes in a WBC heavyweight elimination.

WBA junior heavyweight champion Ossie Ocasio vs. Randy Stephens.

The boxing show can be seen in the Washington, D. C., area on closed-circuit television at Capital Centre, starting at 9 p.m. Super TV, a Baltimore/Washington-based subscription service, also will carry the card as a "pay-per-view" event