Marshall has remained on the fringes of the squad over the past two months, and Wolves are allegedly prepared to listen to offers for the versatile 26-year-old.
According to the Daily Star, that has led to both Cardiff and Sheffield Wednesday monitoring the player's situation at Molineux ahead of possibly making an offer.
However, Wolves may opt against selling to a direct rival, with Cardiff currently in second place in the table and seven points behind the West Midlands outfit with a game in hand.
Wednesday could prove to be an attractive option to Marshall having previously spent time in the North of England, but Owls boss Carlos Carvalhal is currently fighting to save his job at Hillsborough.
Marshall has played just three minutes of football since Wolves' 2-1 defeat at Queens Park Rangers on October 28.