McAllister limped off after catching a 1-yard pass and going down awkwardly with about eight minutes left in the half. He was checked out on the sideline, then headed off for further treatment.
In his postgame press conference, Saints coach Sean Payton said he would elaborate further on McAllister's injury Tuesday.
McAllister suffered a torn ACL in his right knee during the 2005 season, limiting him to just five games that year.
He came back strong last season however, missing only one game and rushing for 1,057 yards. It was the fourth 1,000-yard sesaon of his career.
Copyright 2007 by The Associated Press