What prevents a player/team from agreeing to a long-term contract after the franchise tag deadline?

Question

This afternoon is the NFL franchise tag deadline. I keep hearing radio hosts talking about it as the deadline to sign a long-term deal. However, I was under the impression that once this deadline passes, the tagged player is under contract for one year, and that any player under contract with a team could agree to and sign a new contract or a contract extension with that same team at any time, 365 days a year.

So what rule prevents a tagged player from taking the one-year franchise tag tender and continuing to negotiate with their team after today for a better deal before the season starts, even if it is merely a contract extension? And when can they agree to a long-term contract: after the season, free agency next year, or some other time? Or am I being misled here, either by the terminology I'm hearing on the radio or by my own assumptions?

Answer 1

It is of course the Collective Bargaining Agreement...

From Article 10. Section 1.

The player so designated may be one who would otherwise be a Restricted Free Agent. Except as set forth in Section 2(a)(i) below, any Club that designates a Franchise Player shall be the only Club with which such Franchise Player may negotiate or sign a Player Contract during the period the player is so designated, notwithstanding the number of his Accrued Seasons. The period for Clubs to designate Franchise Players will begin on the twenty-second day preceding the first day of the new League Year and will end at 4:00pm New York time on the eighth day preceding the first day of the new League Year.

The Franchise Tag is essentially a one-year contract and is very strict and well defined within the CBA. If no other deal can be made prior to the deadline the amount and term of the tag takes effect. Since you can't extend a Franchise Tag there would not be any ability to alter the deal once signed.

From Article 10. Section 9.

A Club may designate a Franchise Player only during the periods and in the numbers specified in Section 1 above; otherwise, the Club’s right to such designation expires. However, a Club may designate a player to whom the Club has rights as a Franchise Player with respect to any first future League Year during the term of this Agreement for which such player is anticipated to be an Unrestricted Free Agent. For any such players, the Club shall be deemed on the first day of the first future League Year in which the designation takes effect to have automatically tendered the player a one year NFL Player Contract...

The NFL's website puts this in a less "legalese" way:

July 16: At 4:00 p.m., New York time, deadline for any club that designated a Franchise Player to sign such player to a multiyear contract or extension. After this date, the player may sign only a one-year contract with his prior club for the 2018 season, and such contract cannot be extended until after the club’s last regular season game.