Quarterback Ken Stabler won't be disciplined by the National Football League if he keeps his distance from "undesirable elements," Commissioner Pete Rozelle said yesterday.

When he was with the Houston Oilers, Stabler was the subject last year of an NFL investigation following published reports that he was associating with known gambling figures.

Stabler was released by the Oilers this year. The New Orleans Saints have expressed interest in signing him as a backup quarterback to Archie Manning because Dave Wilson is out for the season with a knee injury, though the Players Association's lack of a contract prevents the Saints from negotiating with Stabler.

Rozelle's statement released by the NFL said in part:

"After a review of all information available to me following an extensive investigation and a private meeting with Ken Stabler, I have concluded that disciplinary action is not merited and that he should be free to sign a contract with an NFL club should he so desire.

"In so doing, I have cautioned him that any return to the NFL is conditioned on his future willingness and ability to maintain total separation, both publicly and privately, between himself and any undesirable elements . . ."

A physician who will be assisting when former New York Giants running back Doug Kotar undergoes brain surgery today says the operation "is just as frightening as it sounds." Kim Sloan, the orthopedic specialist retained by the Giants, said Kotar's family requested he not reveal details of the recently retired player's condition until surgery has been completed . . .

St. Louis Cardinals linebacker E.J. Junior pleaded not guilty yesterday to charges of possessing cocaine and marijuana.

The former Alabama star did not appear at a brief hearing at which his attorneys entered the plea and waived arraignment. The case will be presented to a Tuscaloosa County, Ala., grand jury, which has indicted four other men in the case.