The Bucs reported to training camp Wednesday. They begin practice Thursday.
Demps was obtained from New England in a trade that sent running back LeGarrette Blount to the Patriots in April. The former Florida running back was a silver medalist as part of the United States' 400-meter relay team at the 2012 London Games.
Demps was not selected in the 2012 draft because he told teams he wanted to focus on his track career. He later signed with New England, but did not appear in any games.
The Bucs signed guard Jeremy Lewis on Wednesday and said punter Michael Koenen was placed on the active/non-football injury list with a toe injury.