Preparing for tonight's 7:30 game at Capital Centre against the Indiana Pacers, the Washington Bullets received decidedly mixed news on the medical front.

Forward Rick Mahorn, after missing three games because of a tender left ankle, practiced with the team yesterday at Bowie State College and was declared fit. Guard Gus Williams, however, will not be able to return to action. The Bullets' scoring leader is still hampered by what team doctors have determined to be a strained adductor tendon in his right groin.

Williams is undergoing daily treatment incorporating heat, stretching and electrical stimulation at the Sports Medicine Center in Chevy Chase. His status for Saturday night's game against the Los Angeles Lakers remains questionable. Williams' injury could be easily confused with the more common strained abductor muscle. The difference is that the strain on the tendon is toward the body's median axis for the adductor as opposed to away from it for the abductor.

Bullets Coach Gene Shue feels Williams will be missed, although the Bullets beat Detroit with him hobbled for most of last Friday night's game and won the next night over Milwaukee while he watched in street clothes.

Shue felt that in both games, particularly the one with the Bucks, his club could have taken control sooner with a healthy Williams. "We just would have been more explosive," the coach said.

Williams didn't care to speculate on any difference in the team without him. "We won both games, which is the most important thing," he said.

The Pacers, 5-14 for the third-worst mark in the NBA, have had little to cheer about. One bright spot for first-year Coach George Irvine has been forward Clark Kellogg. After missing the first five games recovering from preseason arthroscopic knee surgery, the third-year player from Ohio State has emerged as Indiana's leading scorer. He also has provided needed help on the boards with more than eight rebounds per game, including 21 in one game against Milwaukee.

Kellogg only recently cracked the starting lineup, replacing Tony Brown, who made the team after an open tryout -- "the Walter Mitty camp" -- for players last summer. Brown, cut by the New Jersey Nets in 1982, is averaging better than 11 points a game, one of seven Pacers who scores in double figures.

"Every NBA team should have a Tony Brown on its roster," said an impressed Irvine.