
Walters missed the 1-1 Championship draw with Blackpool at the weekend with a stomach bug while fellow forward Lisbie picked up a back condition in the warm-up.
Physio Matt Byard told the club's official website: "Kevin tweaked his back and had to have treatment and we couldn't put him on. We will have another look at him but he is obviously a concern for us."
Magilton has come under heavy criticism after seeing Town slip to seven points off the top six and a win over Forest at Portman Road is vital to keep their flagging play-off challenge alive.
Argentinian winger Luciano Civelli made his debut at the weekend and should continue on the left while Ben Thatcher returned behind him in place of Pim Balkestein.
Midfielders Alan Quinn and David Norris are both available after missing the Blackpool draw through suspension and will be in contention but full-back Moritz Volz remains sidelined with his groin problem and Ivan Campo is also out with a torn calf muscle.

Bristol City boss Gary Johnson has dismissed suggestions his side do not deserve to be challenging for a play-off spot in the Championship.City have won their last five games and are unbeaten in the league since before December.
Burnley midfielder Chris McCann admits he would love to win full international honours with the Republic of Ireland.The Dubliner was sent home by Ireland Under-21s in November 2007 for refusing to be on the bench after being named among the substitutes.
Swansea's Dorus de Vries feels the fearless nature of opponents means English football is the toughest place to be a goalkeeper in the world.A scruffy set-piece goal denied the Swans an FA Cup win over Fulham last weekend and the 6ft 1in Dutchman is wary of the direct tactics often adopted in England.