Free agency is 5 1/2 weeks away, but Jeremy Lin’s agent already is setting the groundwork for what could be a complicated negotiation.

Roger Montgomery, in a rare interview, told The Post nothing is assured regarding Lin’s Knicks future, despite interim coach Mike Woodson’s declaration the global phenom — who becomes a restricted free agent on July 1 — would “absolutely’’ return.

When asked if he expects the Knicks negotiation to be cut-and-dried, Montgomery forewarned: “I don’t expect that. We’re not anticipating that’s going to happen. We don’t have assurances of anything. I know history shows most restricted free agents go back to their team, but I’m not going to assume anything. We’re waiting to see what happens.’’

Montgomery’s emphatic remarks — coupled with Lin’s “nothing’s set in stone’’ comment on Trash Bag Day — seem to be strategic messaging.

There is a possibility the Knicks will force Lin, 24, and his reps to find the point guard’s market value by first signing an offer sheet from another team, which must project Lin’s potential from a 26-game window when he played starter’s minutes.

Lin, who made $762,000 this season, also must find a club that feels the Knicks won’t match the offer. The good news for Montgomery is in the new collective bargaining agreement, teams have just three days to match an offer, less than the prior seven-day window that hamstrung teams.

Montgomery must create the impression the Knicks are not locks to retain Lin to spur teams to present an offer sheet. A source confirmed Toronto, which has a large Chinese population, will be one suitor.

The Knicks ultimately control Lin’s destiny because they cannot be outbid. And if the Players Association wins its arbitration hearing and restores Lin’s early Bird rights, it is a virtual certainty the Knicks will match any offer because the Bird exception means teams can exceed the salary cap to re-sign players.

That would allow the Knicks to keep their $5 million mid-level exception to sign a solid, veteran point guard from a list that starts with Steve Nash but also includes Jameer Nelson, Andre Miller, Ramon Sessions, Lou Williams and Raymond Felton.

A source said the arbitration hearing date will be set this week. If the union loses and the Knicks need their $5M mid-level exception to re-sign Lin, it could get trickier.

Under the CBA, teams under the cap — such as Toronto — can offer Lin the league’s average salary of about $5M for the first two years, then jack the third and fourth years to the maximum of $15 million. The club is permitted to do so only if it is far enough below the cap to take in the average wage of Lin’s four-year offer. Such a “back-loaded offer’’ causes concerns for the Knicks, who by the third year of Lin’s contract would be well over the luxury-tax apron of $74 million, costing them a heavy tax and their full mid-level exception as a taxpayer.

However, the financial boon of having Lin as a Knick for the next four years may be too sweet to consider future luxury-tax penalties. The Knicks’ merchandising in the U.S. and Asia may go through the roof as owner James Dolan looks to recoup the $850 million he invested into the Garden transformation. Lin’s No. 17 jersey was the second-biggest seller in the NBA for the year despite only being available from February on.

On the basketball side, Lin plays the position at which the Knicks are neediest. If they are comfortable his rehab from a torn meniscus finishes well, it will be tough for them not to match, even for their entire $5M mid-level exception.

Montgomery said Lin is in the final stages of his rehab and will head to his native Northern California soon.

“He’s doing well, trying still [to] get stronger and heal,’’ Montgomery said.

The hope is for Lin to participate in July’s Olympic training camp as a member of the U.S. Select Team that practices against Team USA. However, if he is still unsigned, that could be curtailed.

“It hasn’t been settled, but he’d be excited to do it,’’ Montgomery said.