Sanders, a two-time Pro Bowler, tore his left bicep against the 49ers last weekend and will need surgery.
Sanders had just returned to the Colts' lineup two weeks ago. He had missed all of training camp and the first five games of the year after undergoing offseason knee surgery. He has missed 40 of 87 games during his injury-plagued, six-year NFL career.
Indianapolis' other veteran cornerback, Kelvin Hayden, is also expected to be sidelined for the next three to four weeks after he suffered a sprained knee during the 18-14 win over San Francisco. Hayden is not expected to undergo surgery.
"Not real sure (how long Hayden will be out)," coach Jim Caldwell said. "We're kind of looking at probably a three to four week window."
The Colts (7-0) host AFC South rival Houston (5-3) this Sunday. Texans quarterback Matt Schaub and receiver Andre Johnson will likely be looking at a Colts defense with two rookies
- Jerraud Powers and Jacob Lacey - starting at cornerback. Three-year veteran Melvin Bullitt will take Sanders' place at strong safety.
"(Sanders and Gonzalez) are fine football players, great leaders and members of our team," Caldwell said. "The thing about it, though, we've had young people step up and do a great job in their absence. We'll continue on that path."
Wide receiver Anthony Gonzalez, meanwhile, underwent arthroscopic surgery Thursday to clean out loose particles in his right knee. Gonzalez suffered a sprained ligament in the knee during the Colts' season-opening win over Jacksonville. A date for his return has yet to be determined.
