Brown (hip) has been ruled out for Monday's game against the Hawks, Taylor Snow of the Celtics' official site reports.
Brown tweaked his hip during the third quarter of Friday's win over the Hornets and was sidelined for Saturday's rematch. He'll remain out Monday, opening up a few more minutes for Jordan Walsh, but the Celtics opted for a big lineup Saturday, starting Al Horford and Luke Kornet while Payton Pritchard played 29 minutes off the bench.