Every once in a while, a reminder emerges that, in the NFL, a deal isn’t done until the deal is done. Sometimes, however, a deal that isn’t done becomes undone in a way that pisses people off.

Ian Rapoport of NFL Media explains that the intention of receiver Emmanuel Sanders to sign a contract with the Broncos on Sunday occurred after his agent, Steve Weinberg, accepted a deal in principle with the Chiefs. Weinberg is specifically accused of “shopping the Chiefs offer” to the Buccaneers, without explaining that he’d told the Chiefs the terms had been accepted. Thereafter, Weinberg agreed to terms with the Broncos.

Per Rapoport, the 49ers also are upset because Weinberg agreed to send Sanders to San Francisco for a visit before “blowing it off.” (That’s hardly uncommon, though.)

“When a man gives you his words and pulls out then gives another team your word and pulls out, then gives another team his word. . . . Not proper,” an unnamed executive told NFL Media.

That quote creates the impression Weinberg agreed to terms with two other teams before agreeing to terms with the Broncos. It’s unclear, however, whether an agreement in principle was reached with the Buccaneers.

“This was one of the worst situations in modern football negotiations,” an unnamed executive from an unnamed team involved in the situation told NFL Media. “Totally wrong. This needs to be stopped.”

(Actually, it’s probably much worse for a team to agree to terms with a player, to tell him that he passed his physical, and then to decide that he failed his physical.)

There’s an easy way to stop it. Teams who get burned by agents who engage in allegedly unscrupulous practices should simply refuse to do business with those agents. While Weinberg and Sanders had every right to renege on agreements that were not legally binding — and they’re not legally binding until the paperwork is signed (which perhaps should make the Broncos a little nervous) — there’s an unwritten code in every industry that allows business to be transacted efficiently and reliably.

Those who violate that code have a harder time transacting business in the future. But instead of merely deciding quietly to put Weinberg on an internal list of agents who can’t be trusted (it’s likely not a short list), someone has opted to smear Weinberg broadly by complaining publicly (but anonymously, of course) about Weinberg and apparently by pointing out to NFL Media the details of Weinberg’s decertification by the NFLPA that occurred more than a decade ago, for reasons unrelated to negotiation tactics or practices.