Detroit Pistons center Isaiah Stewart will be reevaluated in 3-to-4 weeks after an MRI revealed a left shoulder impingement, the team said Thursday.Stewart, 21, has not played since Feb. 25. The timeline given by the Pistons puts the remainder of his regular season in jeopardy.Stewart is contributing a career-high 11.3 points to go along with 8.1 rebounds through 50 games (47 starts) this season.