Gates has not missed a game this season and has amassed 40 receptions for 663 yards and nine touchdowns.
San Diego will also be without kicker Nate Kaeding, who will miss his third straight game with a groin issue.
For the rest of the Chargers' roster, linebacker Brandon Siler (foot) is listed as doubtful, while linebacker Larry English (foot) and receiver Richard Goodman (hamstring) are questionable. Linebacker Kevin Burnett (shoulder), guard Kris Dielman (neck) and cornerback Quentin Jammer (not injury related) are probable.
The Associated Press contributed to this report.