Stevens told reporters in his pregame availability that Walker continues to be sore but that Williams has showed slight improvements.
Boston trails the series 3-1, after the Celtics -- minus Walker and Williams -- lost Game 4 at home 141-126 on Sunday night.
Walker is dealing with a bone bruise in his left knee that he suffered in Game 2. Williams left Game 3 with a sprained left ankle and has been dealing with turf toe for several weeks.
Their absence was felt Sunday night, as the Celtics struggled despite a 40-point performance from Jayson Tatum.