Colts free safety Sanders won't play against Broncos

Pro Bowl free safety Bob Sanders, who hasn't played since undergoing arthroscopic knee surgery last month, will miss a fifth straight game on Sunday, when the Indianapolis Colts face the Denver Broncos.

The team's most physical player in the secondary, Sanders has been downgraded to "out," after suffering swelling and discomfort following attempts to practice this week.

It is likely that 2005 first-round choice Marlin Jackson, who got most of the work at free safety with the No. 1 offense Thursday and Friday, will be the starter alongside rookie strong safety Antoine Bethea. The playing time of second-year veteran Matt Giordano, who most often plays on special teams, probably will be increased in nickel and dime situations.

The Colts will be using their fourth different starting combination in the secondary for the showdown with the Broncos.

Jackson played one season at safety at the University of Michigan, and plays a similar role in his duties in the Colts' nickel packages. There was speculation in training camp that Indianapolis might move Jackson to safety, where he would compete for a starting job, but the coaches kept him at cornerback. Some league personnel feel that safety is Jackson's more natural position.

When Sanders underwent the arthroscopic surgery in mid-September, it was believed he would miss three or four weeks. Mike Doss filled in admirably the past four games, but then suffered a torn anterior cruciate ligament in last Sunday's victory over Washington, and was placed on injured reserve.

The Colts this week were forced to re-sign third-year veteran Dexter Reid, who played with Indianapolis in 2005 but was released toward the end of training camp this year, to bolster the safety position.

Len Pasquarelli is a senior writer for ESPN.com.