Free agent Bubby Brister signed a one-year contract yesterday with the Philadelphia Eagles to back up starting quarterback Randall Cunningham. The Eagles needed a successor to Jim McMahon, who left Philadelphia and signed a free-agent contract with the Minnesota Vikings. The 6-foot-3, 207-pound quarter back played six games for the Pittsburgh Steelers last season, starting the last four regular-season games after Neil O'Donnell was injured. * BEARS: Defensive end Richard Dent, Chicago's career sack leader and the Most Valuable Player in the 1986 Super Bowl, could become a free agent after this season. Chicago player contract negotiator Ted Phillips said Dent would gain free agency if he meets certain, unspecified performance incentives. * BENGALS: Mark Duper, the wide receiver who starred with the Dolphins for 11 years, has agreed to play for Cincinnati. According to today's editions of The Cincinnati Enquirer and The Miami Herald, sources close to the negotiations say Duper has agreed to a one-year contract worth about $1 million. * BILLS: Pro Bowl defensive end Bruce Smith ended his holdout by reporting to training camp, saying this could be his last season with Buffalo. Smith, bitter over the absence of a new contract, is in the last year of a contract that pays him $1.6 million a year. He is seeking a deal that would pay him $4 million a year. "As of right now, I feel this will be my last year with the Buffalo Bills . . . unless they can work something out," he said. * BROWNS: Fullback Kevin Mack, in an emotional farewell, retired after eight seasons. "It's been a great eight years playing," Mack said, dabbing his eyes with a tissue. Mack led the Browns in rushing in six of his eight seasons. His most productive year was 1985 when he gained 1,104 yards on 222 carries. * BUCCANEERS: Wide receiver Lawrence Dawsey, who insisted signing a short-term contract as a rookie, cashed in on his decision, signing a four-year contract. * CHARGERS: General manager Bobby Beathard says San Diego may be close to signing quarterback Stan Humphries to a long-term contract. "His agent has submitted another proposal," Beathard said. "We weren't that far off from the beginning." * COLTS: Faced with the defection of Jeff George, the club is reportedly close to signing Don Majkowski, a former Pro Bowl quarterback with the Green Bay Packers. "I think it's something we're going to get done in the next 24 hours," said general manager Jim Irsay. The decision to seek another quarterback was prompted by George's absence from training camp. He is seeking to renegotiate his contract, and fines against him total $20,000. * COWBOYS: Emmitt Smith, the NFL's leading rusher, is holding out for a $4 million annual salary, so Dallas is holding auditions for running backs. Mike Beasley impressed coaches on Sunday in the annual Blue-White scrimmage. Beasley, who played wide receiver at West Virginia and was on the Cowboys' practice squad last year, gained 47 yards on 14 carries and scored on a 12-yard run. * DOLPHINS: Miami fans attending the opening practice knew they were in the right place thanks to a couple of landmarks -- Don Shula and Dan Marino. The surroundings were different, though, and not just because of the Dolphins' move to a new complex at Nova University in Davie, Fla. Miami has new receivers, two new offensive linemen and a new fullback. * 49ERS: Pro Bowl running back Ricky Watters may abandon his pursuit of more money this season for the prospect of a bigger contract a year from now. Agent Blaine Pollock said that Watters is close to accepting San Francisco's minimum contract tender, which would mean a one-year deal followed by restricted free agency in 1994. * GIANTS: Nose tackle Erik Howard and defensive end Eric Dorsey missed practice with back problems, but New York coach Dan Reeves didn't think either injury was serious. Reeves said he was cautiously optimistic after seeing linebacker Lawrence Taylor practice for the first time since rupturing his Achilles' tendon last season. * LIONS: "It was a small accident I regret," linebacker Darryl Floyd said after tackling running back Barry Sanders. Sanders was not injured and not upset over the mishap. But Detroit coach Wayne Fontes reiterated his policy regarding the team's franchise player. "The players got the message," Fontes said. "We can't hurt Barry and they understand that." * RAIDERS: Patrick Bates, the team's first-round draft choice, signed a five-year contract worth $4,739,500.