Cable said Gradkowski has a sprained shoulder and was undergoing an MRI on Monday to determine the extent of it.
Campbell made the most of his second opportunity with a well-played second half that won over the fans who booed him from almost the start of his Oakland career because they preferred Gradkowski over the player brought in from the Washington Redskins to replace draft bust JaMarcus Russell.
"It's been a long year already for me," Campbell said. "It started back from the time I was traded. Starting the season off, I was putting too much pressure on myself to make all the plays because of the high hopes for me this season instead of just relaxing and playing the game and let the game come to you. I tried to force the game. That's one of the things I learned over the weeks when I was sitting out and doing the self evaluation on myself and getting to learn the offense a little better."
Campbell spent his two weeks on the bench doing a "self evaluation" of his early season play. He went 30-of-52 passing for 267 yards and one touchdown with two interceptions before being benched. He took six sacks and led the Raiders to just 16 points.
Campbell didn't get off to a much better start in his return to the field. The Raiders punted without recording a first down on the first two series in which Campbell played, before driving for a field goal at the end of the first half.
After a brief drive by Gradkowski at the start of the third quarter, Campbell went back out and wasn't able to generate a first down on his initial drive of the second half. Then he finally showed why the Raiders traded for him during the offseason to replace Russell as the quarterback whom Oakland looked to build around.
"When you can get that kind of production from a guy who's been standing for a couple weeks now and then comes out and gets into rhythm like that, that's what you're hoping for," Cable said. "A job well done by him but by everybody on offense during those two drives."
Campbell needed to take only one more snap, a kneel-down that capped Oakland's first victory over its AFC West rival since 2003.
This marked the third consecutive Raiders win in which the winning score was generated by the backup quarterback, including Russell's comeback in Denver last season after Charlie Frye was injured.
Cable said he'd prefer not to make in-game changes, but he pointed out the Raiders had success in the past with it when George Blanda led comebacks in relief of Daryle Lamonica.
"There is some history there," Cable said. "So it's not like it hasn't been done here before. You'd like your quarterback to be able and go out and consistently do it. We've had two situations now where it worked in our favor, but again, I just think it's a good problem to have two quality players."
Notes: Cable said Darren McFadden's injured hamstring is improving and that he would have a better idea Wednesday if the running back would be able to return this week. ... Cable said there's a "great chance" that OL Robert Gallery could return for the first time since injuring his hamstring in the season opener. ... WR Chaz Schilens isn't close to returning from a knee injury that was supposed to have healed by now.
Copyright 2010 by The Associated Press