When does voluntary mean mandatory? When a sum of $3 million is at stake.

At least that’s the way the Jets seem to view things in their latest dust-up with unhappy cornerback Darrelle Revis. The team’s voluntary off-season conditioning workouts begin a week from today, and the Jets will require Revis to show up if he wants to eventually collect his workout bonus, according to a league source.

Revis is in Arizona, doing ongoing rehab on his left knee, which was surgically repaired last October after he suffered a torn ACL on Sept. 23. But the team wants to monitor his rehab once the conditioning workouts start, even though it’s possible he could be traded before the NFL Draft, which begins April 25.

Revis, who is seeking a lucrative long-term deal, is expected to comply. His contract calls for three separate bonuses of $1 million before the season begins, but the language of the deal ties them together. Those bonuses are $1 million in March for still being on the roster, $1 million in June for attending the workouts, and $1 million in July for reporting to training camp. If he fails to fulfill one or more of those, none of the bonus money will be paid.

Tampa Bay reportedly has emerged as the only suitor, but for a trade to be done this month, the Buccaneers would want to give Revis a thorough physical to see how his rehab is going, and how close the superstar corner is to returning to the field. Revis is in the last year of a four-year deal, and language in the contract prevents the Jets from using the franchise tag on him next year, so he would be a free agent.