Campbell's broken collarbone with the Raiders midway through the 2011 season had deep reverberations in Cincinnati.
The injury prompted then-Raiders coach Hue Jackson to lobby for a trade with the Bengals, who sent them Carson Palmer for a first-round pick and a conditional second-round pick. Palmer was holding out, saying he'd never play again for the Bengals.
Bengals owner Mike Brown was inclined to keep Palmer and make him sit out. The generous offer from Oakland forced him to reconsider.
The Raiders got the trade but failed to reach the playoffs, Jackson was fired and Campbell moved on to Chicago. Jackson was rehired as an assistant in Cincinnati and was elevated to offensive coordinator when Jay Gruden left for Washington after last season.
Campbell's familiarity with Jackson was attractive to both the quarterback and the Bengals, who decided to sign their third backup in the last three years.
''He reached out to me but he didn't want to be the forefront guy that was pushing this,'' Campbell said. ''He wanted the other coaches to make sure they were on board to make the right decision.
''I came in for a visit and was able to connect, and I liked everything and the direction it was going in.''
Campbell started his nine-year career with Washington. He also has played for Oakland, Chicago and Cleveland, where he started eight of the Browns' last nine games last season.
Dalton has been durable during his three seasons in Cincinnati, with Bruce Gradkowski and Josh Johnson getting little playing time. Johnson was the backup last season and got into two lopsided wins at the end, but didn't throw a pass.
The Bengals have reached the playoffs in all three of Dalton's seasons and lost in the first round. Dalton has struggled in two playoff losses at Houston and a 27-10 loss at home to San Diego last season.
The Bengals think Campbell's familiarity with Jackson's coaching methods can benefit Dalton in the transition to a new coordinator. Jackson is expected to emphasize the run more next season.
''If he asks a question of what Hue is thinking or how did you do this before, I think those are some aspects that I can help him along with because of some of my experience within the offense,'' Campbell said. ''That really pays dividends.
''On the other side of it, this is a big year for him coming up. I can help with film study and being an extra set of eyes.''
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