The Detroit Lions have asked retired running back Barry Sanders to return $7.3 million of an $11 million bonus he got when he signed his contract, the team said.

Lions Vice President Chuck Schmidt sent Sanders a letter requesting he return the money this week. If the Lions don't get a response by the start of the NFL season Sept. 12, Schmidt said the Lions will file a grievance with the NFL Management Council and NFL Players Association.

An arbitrator would hear arguments and rule upon the grievance.

"The contract language says that as a condition, he must report, play, practice and not leave the club without permission for each of those years. In the event he does, he's in default," Schmidt said.

Sanders signed a six-year contract in 1997 that paid him $11 million in up-front cash. The $7.3 million represents the two-thirds of the contract left unfulfilled.

Lamont Smith, Sanders's agent, said the bonus was paid for signing the contract, not for completing the contract.

"It's a gray area," Smith said. "We are waiting for some type of authority to suggest he has to do it. If he has to pay it back, then Barry wants to. If not, nobody wants to give back $7.3 million."

Sanders retired July 28, just 1,467 yards short of breaking former Chicago Bears running back Walter Payton's career rushing record of 16,726.

DOLPHINS: Running back J.J. Johnson may have to wait a little longer to make his NFL debut. Miami's top draft pick re-injured his left hamstring in practice Tuesday and likely will miss Saturday's preseason game against the Lions.

Johnson strained his hamstring in a scrimmage Aug. 7 and has practiced little since. The injury has kept Johnson from contending for playing time with incumbent running back Karim Abdul-Jabbar and rookie Cecil Collins.

CARDINALS: Guard Ernest Dye has regained some nerve function in his right arm that was mangled in a rollover accident, doctors said.

However, physicians were unsure whether Dye ever will regain full use of his arm because of the extreme nature of the injury, which likely has ended his NFL career.

Dye's arm was nearly severed in the Aug. 16 crash about 25 miles south of Flagstaff, Ariz., where the Cardinals hold training camp.