Rick Mahorn missed another practice yesterday because of his sore ankle and, although he's expected to start for the Bullets tonight in Denver (9:30, WDCA-20), he'll have a tough time keeping up with Dan Issel.

Issel, one of the league's most mobile centers, scored 25 points in the Nuggets' 124-115 victory over the Bullets Feb. 7 at Capital Centre, when Mahorn was at full strength.

"He does a lot of running," Mahorn said of the high-scoring center as he gingerly tested his ankle on the sideline while his teammates were working on defending against Denver's passing game. "He fills a lane just like a forward."

Mahorn injured his ankle in the second quarter of a 100-98 victory over Kansas City last Friday and sat out Sunday's overtime decision over New York. He had 11 rebounds while playing 42 minutes in Tuesday night's loss to New Jersey, but was favoring his leg. Nets center Len Elmore, an eight-point-a-game scorer, had 18 points.

"I couldn't jump off my right leg," Mahorn explained. "The leg is still sore and it hurts when I come down on it. I guess playing against the Nets didn't help it, but I really wanted to play. That was an important game."

Coach Gene Shue still hasn't recovered from the defensive breakdown at the end of the first overtime that left Darwin Cook wide open to make a three-point shot that sent the game into the second extra period.

"We just blew that game," he said yesterday. "We were up four points with 46 seconds left. But we missed two foul shots, then somebody (Don Collins) fell asleep on defense. The only way they could tie it was on a three-point shot and we don't even guard their best long-range shooter.

"If we had won that, we'd have a three-game winning streak and everything would be fine. Now, we've got to get something started again."

This quick two-game trip won't be easy. After taking on the Nuggets, who are 18-12 at home, the Bullets will fly to Utah to meet the Jazz, a 113-106 winner at Capital Centre 10 days ago.

If Mahorn is unable to start, Shue again will call on Jim Chones, who had two points and seven rebounds when he filled in against the Knicks. However, Jeff Ruland wound up playing 40 minutes and contributing 18 points.

Spencer Haywood also did not practice yesterday. He said he strained his lower back doing situps the day before, but that it wasn't serious and he would be ready for the Nuggets.

"I'm in my groove now and I just want to maintain it," he said, referring to his three successive outstanding games. Since asserting himself more on offense, the 32-year-old forward has scored 27, 24 and 21 points.

Tonight will be a homecoming, of sorts, for the well-traveled forward. He began his professional career at age 19 with Denver in the American Basketball Association. Against Los Angeles one night (April 15, 1970), he scored 59 points

"We used to play in the old arena downtown," Haywood recalled. "It held 7,000 tops, but we used to pack it."

The Nuggets now play in a 17,251-seat arena, but are having trouble filling it. They are averaging 10,913 a game and there have been repeated reports of financial problems and of a possible merger with Utah.

Denver has fallen to third place in the Midwest Division with a 29-29 record after losing six of its last seven. The Nuggets' strength is their front line of Issel and forwards Alex English and Kiki Vandeweghe, who are each averaging more than 20 points a game.

"They are a difficult team to defend because they're always shooting," said Haywood. "They come down, make one pass and let it go. Some teams set up and make several passes before taking a shot, but you never know when Denver is going to shoot."

When asked on his last trip here about Denver's fast-breaking style of play, which has produced a league-leading 125-point-a-game average, Issel said: "We used to run when it was available. Now we run when it's available, when it's not available and at halftime."