Dockett told the Cardinals after the Super Bowl that he felt he had outperformed the five-year, $22.010 million contract he signed in 2006, the source said.
The team told him then they would not trade him but might consider discussing his contract. No talks on a new deal have occurred this offseason, so Dockett restated his trade request.
Top defensive tackles are making $8 million a year or more, and Dockett, according to the source, would like to be traded in order to receive a top defensive line contract.
His agent, Drew Rosenhaus, declined comment.
The Cardinals have said they plan to work toward extensions with Karlos Dansby and safety Adrian Wilson before they revisit contracts for players with more than one year remaining on their deals. Disgruntled receiver Anquan Boldin, with two years left on his deal, also stands ahead of Dockett. The team's attempts to entertain trade offers for Boldin have so far gone nowhere.
Boldin and Dockett both cited hamstring injuries in missing post-draft practices. Rosenhaus represents both players.
John Clayton and Mike Sando cover the NFL for ESPN.com.