Linebacker Pat Angerer and safety LaRon Landry did not travel with the Colts to San Francisco on Saturday and will miss Sunday's game.
Angerer did not practice Friday and was listed as doubtful. The Colts had already ruled Landry out of Sunday's game because of an ankle injury that kept him out of practice all week.
The loss of two defensive starters is more bad news for Indianapolis (1-1), which lost at home for the first time in almost a year last weekend and has put three offensive starters on injured reserve in less than two weeks. Running back Vick Ballard sustained a season-ending knee injury last week in practice. Left guard Donald Thomas (quad) and tight end Dwayne Allen (hip) were put on injured reserve this week.
AP NFL website: www.pro32.ap.org