Gros was selected in the first round of the 1962 NFL Draft by the Green Bay Packers and in the second round of the AFL Draft by the Houston Oilers. Gros opted for the NFL, where he backed up fellow LSU Tiger Jim Taylor at fullback and the Packers repeated as NFL champions in his rookie season in 1962. He played two seasons in Green Bay, then was traded with hall of fame center Jim Ringo to the Philadelphia Eagles for linebacker Lee Roy Caffey (and a first round draft choice) in May 1964. The draft choice was used to select halfback Donny Anderson as a "future pick" in the