On March 18 at Capital Centre, Mitch Kupchak made perhaps the dumbest move of his athletic life. He reported for work.

Anyone who appreciates the special zest Kupchak brings to an already intensely competitive sport understand why he played that afternoon against the Cleveland Cavaliers, even though his back still throbbed from the night before.

He had played well that night, for the first time in weeks, "until I grabbed a rebound and Elmore Smith pulled me from behind, pulled a muscle or something in my back. I thought I knew my back well (from having surgery similar to Phil Chenier's in college).

"When my back would go out like that before, I'd rest it some and it would get bettere even while I played. Pulls are different. They take more time to heal. But the next morning I felt confident and also guilty."

The guilt came from missing so much prior time with an injured Achilles' heel and playing badly until just before the back injury.

"What it added up to," he said, "was a mistake, because it got worse during the game without anybody touching me. The more I ran, the worse it got. And if I'd been smart, I'd have missed a lot more games in a row."

He missed four games, then returned for six.

"We were going for the best record in the NBA, and it meant a lot to the team and the staff and to me. I could spell Wes (Unseld) and Elvin (Hayes) and almost play as well as them. But I want to play better than them when I come off the Bench-and I couldn't."

When the Bullets achieved their regular-season goal, Kupchak again rested. But there had been enough additional damage so that he did not again feel comfortable on the court until three days ago.

And teammates said that Friday night, in game three of the playoffs against the Hawks, Kupchak gave a Kupchak-like performance for the first time in months.

"Three months," he said. "Yeah, that's accurate. It's been rough; some problems with the injuries and some problems off the court. But a lot of positive things have happened the last week or two."

The nicest was Hawk Coach Hubie Brown's crude praise that "Kupchak kicked our small forward's (butt)" when the Bullets gained the lead for good in the fourth quarter. Specifically, there were three tough rebounds, two free throws and a three-point play.

And then, when he was physically and mentally aglow for the first time in three dozen games, he was on the bench again. It was time for Unseld to return.

"Dick Motta coached the way I would have coached," Kupchak said over breakfast today, "but I was just starting to get rolling. When you're playing poorly, you have a tendency to look toward the bench, to see who's coming in. Instead of being positive, you think negatively. Not last night.

"So I kinda feel I'm back into it. And it never was a matter of losing confidence. Nothing mental. It just was a matter of not being able to do what I wanted to do until Thursday, to play like I could."

So Kupchak is ready for more minutes.Now he must earn them.

"It's the occupational hazard of being a substitute," he said. "Better yet, being a young substitute. Better yet, being a young substitute who knows he can play. Right now, I understand what Dick's doing. I agree.

"I'm ready to play-and also ready to accept not playing, as long as we keep winning. Because as long as that happens, I'll keep getting chances. My time will come. And before last night I didn't merit playing more.

"But as a sub, I need more than five minutes at a time. Or six or seven. To go through warmups, work up a sweat, then sit down for a half hour-or whatever it takes to play the first quarter and a minute or two of the second-and then be expected to do well immediately is difficult.

"If my job was to spell Wes and Elvin, I could do that. But I do much more than that. I do a lot more for the Bullets than spell Wes and Elvin."

Kupchak was flabbergasted that in 15 minutes during game three he had made only three of 10 field-goal tries. He quickly replayed his performance in his mind, thought surely he shot "eight, nine times at the most." Then he saw The Tree.

Wayne (Tree) Rollins is the 7-1 Hawk center who has been playing 9-7 this series, rejecting more Bullets than the celluloid Superman. Tree's limbs have brushed aside two Kupchak shots and caused at least two others to miss.

"I'd go up over my man, (John) Drew, who's much shorter than me," Kupchak said, "but out of the corner of my eye I'd see Tree coming my way. So I'd alter my shot. That air ball you mentioned wasn't really an air ball."

A Tree ball?

"Listen," Kupchak said. "This is not meant as criticism of the Clemson coaches, but that guy has improved more from his first to second year in the NBA then he did from his freshman through senior years of college.

"As a freshman, he was good. As a senior, he was good. The way he's going now-or at least at this rate of improvement-he can be a dominant center in the NBA."

And Kupchak? Where will he be in five years, with the Bullet immediately ahead of him at his best position, Hayes, seemingly indestructible? And Unseld playing so well, and with such enthusiasm?

Kupchak has looked ahead, to the possibility of having to leave Washington to become a starter. But the last few months have taught him not to look more than a minute or so into the future.