The NFL office sent a letter to all 32 NFL teams Monday warning them not to, well, tamper with players during the so-called legal tampering period which began Saturday and runs until the start of free agency Tuesday at 4 p.m.

The NFL said it would investigate clubs who forged contract agreements with prospective unrestricted free agents before 4 p.m. Tuesday against the league's rules. And while the NFL on Monday declined to tell The Miami Herald whether the Dolphins would be among those investigated this is clear:

1. The Dolphins, who have an agreement in principle with probably the biggest free agent on the market in Ndamukong Suh, are in the NFL's crosshairs.

2. The team is taking the threat of sanctions extremely seriously.

The Dolphins have been in utter lockdown for a week since word leaked they would be chasing Suh. But something changed Sunday and Monday. I'm told employees were told they better have zero contact addressing the possibility of a Suh deal with anyone -- much less the media.

And that makes sense because the media blew Miami's cover on the Suh deal.

Yes, although everyone does it, it is going to be hard for the Dolphins to explain to the NFL how ESPN's Chris Mortensen reported an agreement between Suh and the Dolphins on Saturday when no offer was allowed. This will be particularly difficult to explain if Mortensen's report -- of a six-year, $114 million deal with $58 million in guaranteed money and $60 million the first three years -- is accurate.

How could the numbers be out there and be right if the Dolphins weren't exchanging offers with Suh's agent Jimmy Sexton?

(Sexton is an agent for CAAsports. Mortensen is reprensented by the agency).

Anyway, the Dolphins are said to be "nervous" about this and some other negotiations, one agent dealing with the team told me Monday.

No doubt this email obtained by NFL.com had something to do with raising the alarm for a team that's normally secretive anyway:

"Clubs were advised of the rules for the three-day negotiating period in PP-23-15 (attached). These rules include limitations such as that a club cannot make an ‘offer;’ or enter into a written or oral agreement of any kind, express or implied, or make promises or representations of any type concerning the terms or conditions of employment to be offered to any Unrestricted Free Agent for inclusion in a Player Contract after the start of the new League Year; or provide assurances of intent as to the future execution of an NFL Player Contract.

"Clubs were further advised that ‘Any attempt to undermine the purpose of this negotiating period may be considered conduct detrimental to the League.’ At this time, the League office is beginning investigations into a number of reported agreements with clubs. Violations will be dealt with accordingly."

Violations may be sanctions with fines on the club or individuals and may also rise to the level of costing a team a draft pick or picks.

Again, everyone does this. The Jacksonville Jaguars have an agreement with soon-to-be former Dolphins Jared Odrick. The Buffalo Bills have agreed to give LeSean McCoy a contract extension even though they cannot officially trade for him until 4 p.m.

But when the deal agreed to is the biggest one of free agency and Suh's will probably be that ... And when that deal is reportedly done three days before an offer could officially even be made ... And when the entity breaking the story is the biggest media empire in the nation ... That gets the NFL's attention more than Odrick to the Jags.

By the way, the Dolphins have perfectly good reasons to be nervous about this issue for other reasons. If they've even come close to adhering to the rules, Suh has not signed the deal -- even though he was in South Florida. And until there is a signature, there is nothing certain.

Remember that years ago Minnesota defensive tackle John Randle, visiting the Dolphins facility, said he was eager to sign with the team. And during his visit his phone rang. And suddenly he excused himself because, he told his Miami hosts, he was re-signing with the Vikings.

Also remember that running back Frank Gore reportedly agreed on Sunday to play for the Eagles in 2015. And on Monday he changed his mind and is continuing to look for a team.

Finally there is this: It is possible that to veil the fact they had an agreement with Suh that was reported by ESPN, the numbers change somewhat so that all parties can plausibly deny the report of an agreement was correct.

Wouldn't it be interesting if leaking the numbers costs somebody actual dollars to, well, make those leaked numbers wrong?

Welcome to free agency.