( CNN ) -- Donovan played in NFL for 12 seasons . He was elected to NFL in 12 seasons . Donovan led the Baltimore Colts to world championships in 1959 and 1958 . The cause of Dallas 's death was not immediately disclosed .
Donovan played in NFL for 12 seasons . He was elected to NFL in 12 seasons . Donovan led the Baltimore Colts to world championships in 1959 and 1958 . The cause of Dallas 's death was not immediately disclosed .