Washington Bullet guard Phil Chenier was admitted to Sibley Hospital in Washington, D.C., today for treatment of a chronic back injury. He could be hospitalized as long as 10 days.

The Bullets' other starting guard, Tom Henderson, said today he probably would miss another week with a sprained ankle. Henderson hurt the ankle Wednesday night against Golden State.

With Henderson and Chenier out, Bullet general manager Bob Ferry said he was considering signing a free-agent guard for at least a minimum of 10 days and three games, as specified under a new NBA rule this season brought about by the new 11-man roster limit.

The team presently has only three other guards on the roster, Larry Wright, who has the flu, Kevin Grevey, who has a sore neck, and rookie Phil Walker.

In order to add a player, the Bullets would have to put Chenier on the injured reserve list, which would require him to miss at least 10 games.

Among free-agent guards available are ex-Warrior Charles Johnson, ex-Trail Blazer Herm Gilliam, ex-Net Bubbles Hawkins, ex-Cavalier Mo Howard, ex-Buck Rich Laurel and ex-Hawk Ken Charles.

"We don't want to panic but we can't leave ourselves short either," said Ferry, who added that he had at least two other options: "Do nothing or make a trade. No one knows just how long Chenier will be sidelined and that makes it tough to decide what we should do."

The Bullets would be forced into a trade if they were certain Chenier would not be at full strength for the rest of the year. They have two first-round picks in this season's draft to use as possible trade bait.

After tonight's game against Los Angeles, the Bullets will conclude this road trip at Phoenix Sunday. They have home games against Detroit on Tuesday and Chicago on Thursday before meeting the Bulls Friday in Chicago. The earliest the Bullets expect either Chenier or Henderson to return is next Sunday, when they host the Lakers.

Chenier's chronic back problems, according to Lavine, are caused by a degenerative disk in the lower part of his spine. The disc irritates spinal nerves, causing discomfort in his lower back, Lavine explained.

Lavine saw Chenier again today. His back had not improved so Lavine admitted him to Sibley, where he could be placed in traction and given therapy.

Chenier's chronic back difficulties, according to the Bullets, are caused by irregular spacing in the lower part of his spine. The spine cannot properly support all the lower back muscles and he is susceptible to strains and soreness.

Although he has missed games in past seasons because of the back, it has pained him more this year. He hurt it a week before training camp opened in September, and did not appear in any preseason games. However, he hasn't missed any regular-season contests due to the injury until now.

But the combination of the healing process from the preseason injury and difficulties adjusting to what he says were changes in the Bullet offense, kept Chenier from regaining his starting position until just before Christmas.

He started eight games and then pulled a hamstring Jan. 8 against the Nets and hasn't played since. Ironically, the hamstring, according to Lavine, has healed and Chenier had planned to join the team here for tonight's game against the Lakers until his back acted up.

Chenier was averaging 14 points. Since regaining his starting spot, he had five games in which he scored at least 17 points despite sharing playing time with Grevey. The Bullets also thought he was starting to play less tentatively on the court and was moving much more freely on defense.

Henderson said today that when he got hurt, "I thought we'd be O.K. because I knew Philip was coming out here. Now this has to happen."

Henderson said the swelling in his ankle had decreased, but that the injury was still sore.

"I can see myself playing in maybe five or six days," he said. "I can't run on it and I'm not going to come back until I'm completely healed."THenderson previously sprained an ankle during the exhibition season and it was still bothering him when the regular schedule began. But he has not missed a game and is considered by coach Dick Motta to be one of the keys to the team's success.