Mike Triplett of the New Orleans Times-Picayune broke the news on Friday in a series of tweets. Triplett reported that Saints head coach Joe Vitt was unclear about when Sproles would be able to return.
With Sproles out, running back Pierre Thomas will have to handle the heavy lifting in the New Orleans running game. Mark Ingram and Chris Ivory are also likely to see touches, with Ivory on track for his first game of the season. The Saints haven't gotten a great deal of running yards from Sproles anyway; they're averaging a league-worst 72.6 yards per game on the ground.
Sproles has caught 39 passes this season for 440 yards and four touchdowns, among the top contributors on the Saints' offense. His biggest value may have been as a return specialist; Sproles has averaged 28.7 yards per kick return, good enough for seventh-best in the NFL.