If the Addicks line up in a 4-4-2 formation then Adam Matthews, Akin Famewo, Jason Pearce and Ian Maatsen will start in defence front of goalkeeper Ben Amos.
Forster-Caskey, Ben Watson, Matt Smith and Liam Millar will likely make up a midfield four behind the front two of Chuks Aneke and Conor Washington.
The in-form Jayden Stockley moves to the bench with a slight tightness and Darren Pratley is suspended after being sent off on Saturday.
Nathan Harness, Deji Oshilaja, Chris Gunter, Andrew Shinnie, Diallang Jaiyesimi and Ronnie Schwartz join Stockley on the bench.
Charlton: Amos; Matthews, Famewo, Pearce (C), Maatsen; Forster-Caskey, Watson, Smith, Millar; Aneke, Washington
Substitutes: Harness, Oshilaja, Gunter, Shinnie, Jaiyesimi, Schwartz, Stockley