Nat Moore and Tony Nathan, two of the mainstays of the Miami offense for the past decade, and Tony Hill, a one-time star with Dallas, were cut yesterday as National Football League rosters were pared to the 45-player limit. The Chicago Bears put Jim McMahon on injured reserve with the expectation he can help their young quarterbacks develop.

Hill, released by Dallas earlier this year and picked up by San Francisco, was among a group of veterans released by the 49ers. They included linebackers Tom Cousineau and Jim Fahnhorst and running back Carl Monroe, who scored the first touchdown in the January 1985 Super Bowl.

McMahon, who missed the second half of last season with a shoulder injury and underwent surgery late last year, had been expected to go on injured reserve. He will have to miss at least six weeks -- if he were put on after the roster is set, it would be four weeks.

That move at least temporarily kept a spot on the Bears' roster for Doug Flutie. Mike Tomczak has been starting in McMahon's place and Jim Harbaugh, the team's top draft pick this year, had been virtually guaranteed a spot.

Coach Mike Ditka said the offbeat McMahon, with whom he has some conflicts, will spend his time on the sidelines helping him and coaching the younger players.

"Even if I have to make McMahon an assistant coach, I want him to be out there because the Bears will need all the help they can get," Ditka said.

Moore and Nathan were cut as Miami kept three quarterbacks -- Dan Marino, Don Strock and Ron Jaworski.

Moore, a 13-year veteran, was the Dolphins' all-time leading receiver with 510 catches for 7,547 yards. Nathan, an eight-year veteran, is fourth on the team's all-time rushing list with 3,523 yards and second on the receiving list with 373 receptions.

Coach Don Shula said he believed both could still play and might be re-signed if injuries opened up a spot.

Among the other players cut was defensive end Daryl Sims, Pittsburgh's first-round draft pick two years ago.

The 6-foot-3, 285-pound Sims, expected to be a force when he was taken by the Steelers in the first round of the 1985 draft, never lived up to his expectations. In two seasons of spot play, he had just 14 tackles, four assists and two sacks.

"He has strength and speed, but it didn't show up on the field the way we thought it would," Coach Chuck Noll said in declaring that holdover Keith Gary, once of Chantilly High School, had beaten Sims out.

The Cowboys cut kicker Rolf Benirschke, the veteran acquired last week from San Diego; Cleveland released running back Butch Woolfolk; Minnesota cut running back Ted Brown; San Diego cut wide receivers Anthony Hancock and Bobby Johnson and the New York Giants released veteran defensive lineman Curtis McGriff.

The Bears released veteran defensive linemen Mike Hartenstine and Henry Waechter along with punter Maury Buford. Waechter trapped New England quarterback Steve Grogan for safety in the Super Bowl two years ago. Green Bay cut backup quarterback Chuck Fusina, who led the Philadelphia-Baltimore Stars to two championships in the defunct USFL.

Philadelphia traded veteran defensive end Greg Brown to Atlanta for defensive end Mike Pitts, who had been holding out.

Pitts was a first-round draft pick in 1983 for the Falcons and played all 16 games for them last year. Greg Brown was signed by the Eagles as a free agent in 1981. The H.D. Woodson (D.C.) High and Kansas State graduate ranked second for the Eagles in quarterback sacks.

The Los Angeles Raiders placed Lester Hayes, a 10-year fixture at cornerback, on injured reserve with a strained tendon in the left foot that he broke last season. Hayes had started 149 straight games before missing the last two last season.

Another starting cornerback, Perry Williams of the Giants, also went on six-week injured reserve with a neck injury.

Tampa Bay released Don Shula's son, rookie quarterback Mike Shula.

Looking to Sunday's season opener at Washington, Eagles Coach Buddy Ryan replaced Cedrick Brown at left cornerback with former free safety William Frizzell. Terry Hoage returned to starting free safety.

Roynell Young, normally at left cornerback, is still a holdout in the final week before his team faces the Redskins and three-time Pro Bowl receiver Art Monk.

Frizzell "was a corner when he came out," Ryan said. "We think he's got the speed, and he's going against that big No. 81 {Monk}, so he'll do a job on him, I hope."