Jackson, wide receiver Kevin Curtis (knee), running back Brian Westbrook (concussion) and linebacker Akeem Jordan (knee) were ruled out by Reid after Friday's practice. Curtis has been out since the second week of the season.
Tight end Brent Celek, who suffered a sprained thumb last weekend, practiced this week. Reid said Celek should play.
Westbrook will miss his third consecutive game since suffering his second concussion of the season. The running back has missed six games total.
Westbrook visited doctors in Pittsburgh this week, and the news was somewhat encouraging. Still, he remains out indefinitely.
"(Trainer) Rick (Burkholder) has been in contact with the doctors in Pittsburgh," Reid said. "We'll see what happens next week. He's been feeling better, and that's a plus."
Jordan is out for the fourth week in a row. The starting weakside linebacker returned to practice on a limited basis Wednesday and Thursday, but he wasn't on the field Friday.
"He's just not quite ready," Reid said. "He had a little bit of swelling there, so we backed off a bit."
Will Witherspoon remains the weakside starter, and second-year pro Joe Mays is expected to make his second start at middle linebacker.
Jackson's loss also will be felt in the return game.
Seldom-used Reggie Brown, who has just three receptions this year, will be the third receiver.
Maclin also will replace Jackson as the team's primary punt returner. Jackson has averaged 15.5 yards on 21 returns this season, while Maclin has lost four yards on three returns.
"It's important when someone goes down for the next person to step up and play well," Reid said. "That's always been the case."
"Chances are the ball will come my way more, obviously," the first-round draft pick said. "When the opportunity arises you have to seize the moment. In the NFL, careers are short. You have to go for it while you can."
Copyright 2009 by The Associated Press