Kevin Porter almost clinched winning his fourth National Basketball Association assists title last night with 16 against Detroit, and when he wasn't passing off, the small guard found time to score a game-high 24 points as the Washington Bullets beat the Pistons, 108-103, at Capital Centre.

Porter was leading the league in assists, averaging 8.86 a game to 8.81 for second-place Norm Nixon of Los Angeles, before he dazzled the Pistons.

The Bullets end their season tonight against the Cleveland Cavaliers at Capital Centre at 7:35. By winning, they would equal last season's 39-43 record. Only this time, they will not be going on to the playoffs.

Tonight also will be Wes Unseld Appreciation Night, and although the retiring Bullet center and captain hasn't played for three games because of his sore knees, he is expected to suit up for this one.

With Kevin Grevey on the injury list after hurting a hamstring during Friday's 122-107 loss at Indiana, Austin Carr was activated yesterday and rookie swingman Don Collins started for Grevey. Collins made 10 of 11 shots for 21 points and had five assists and two steals.

Most of Collins' points came off the transition and off feeds from the electrifying Porter.

"Collins really played well," said Coach Gene Shue, "especially defensively. He's at his best in a running game. He handles the ball well when he gets in on the run. He can also shoot so well off the run. He likes to take the ball to the basket."

The final score was misleading. The Bullets led all the way and were ahead by 18 at one point in the second half. The Pistons had only eight men in uniform.

Porter has downplayed winning the assists crown, but last night he went deep into his bag of tricks and his behind-the-back, between-the-legs, look-one-way, go-the-other passes had the crowd of 12,622 roaring approval.

As happy as he was with the way Porter and Collins played, Shue was most pleased with Rick Mahorn, who is expected to replace Unseld at center next season. In the 6-foot-9 rookie's fourth straight start, he scored only seven points but had a game-high 11 rebounds, three assists, three steals and two blocked shots.

"For the last four or five games I've set some goals for Rick," Shue said. "They've been simple goals like running the court, helping out on defense and rebounding. He's been doing great at all three.

"Wes rebounded, made the outlet pass and played excellent defense on his man, but didn't run the court particularly well. That was just Wes. Rick has to run the court to be effective. It's an invaluable asset to a team when the center gets back on defense and runs the court.

"Rick will do fine offensively. There's no problem there. We're trying to teach him winning habits now. We're really going to work with him this summer and make him a player. I'm pleased with him so far. I have confidence that he'll be okay because he's so willing to do the work."