Published: Jul 30, 2010 1:16 AM EDT
Updated: Jul 30, 2010 4:30 AM EDT

MIAMI (AP) — Former Miami Dolphins star Mercury Morris is suing the NFL Retirement Board, alleging he's being underpaid $3,000 a month in benefits.

The lawsuit, filed Thursday in Miami's federal court, claims Morris is receiving $3,100 a month when he should be getting twice that amount. He's also seeking $91,000 in back pay.

Morris won a settlement with the board in 1991 for $250,000 in disability claims.

The NFL Retirement Board is jointly administered by the NFL and NFL Player's Association. An NFL spokesman declined comment, and a message left for the union late Thursday was not immediately returned.

Morris played eight seasons for the Dolphins and San Diego Chargers — most notably as a member of Miami's 1972 undefeated championship team.