Mullins, who has missed only two games in his career to date, leads the Missouri Valley Conference in assists and recently became just the second player in league history to surpass 500 career assists and 250 career steals.
Last season, Mullins missed the postseason NIT games against Oklahoma State and Arizona State, due to a stress fracture in his left leg. He spent much of the off-season rehabilitating the injury.
Mullins' right foot began to bother him in mid-January, although its effects were not immediately seen on the court. As recently as last Wednesday, Mullins had one of the best games of his career with 13 points, 10 assists and five steals. He struggled Saturday in Evansville, however, making 1-of-5 shots.
Lowery said the injury will be re-evaluated by doctors in several weeks, and he left open the possibility Mullins could return.
The Downers Grove, Ill.-native has been a mainstay in SIU's starting lineup the last four seasons. He made his first-career start as a freshman on Nov. 26, 2005, and started 97-straight games prior to last season's injury.
He ranks among the career leaders in numerous categories at Southern, including assists, steals, 3-point shooting, career starts and minutes played. Last season, he was named the MVC Defensive Player of the Year and second-team all-conference.
Off the court, Mullins is a finance major with a perfect 4.0 GPA. He was named an ESPN The Magazine CoSIDA Second-Team Academic All-American in 2008.
In place of Mullins, sophomore Justin Bocot is expected to make his first-career start when SIU hosts Illinois State on Wednesday.