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The Kansas City Chiefs were negotiating a trade for Seattle Seahawks safety Earl Thomas before he suffered a season-ending leg injury in Sunday's 20-17 win over the Arizona Cardinals, Yahoo Sports' Terez Paylor reported Monday.

"The Chiefs, in particular, were particularly annoyed with the development, as sources tell Yahoo Sports that although the two teams couldn’t agree on a trade this past week, the two sides were inching closer toward a deal and there was internal optimism something would be struck before the deadline," Paylor wrote.

According to NFL Network's Ian Rapoport, Thomas suffered a "clean, lower leg break" that will rule him out for the rest of the regular season.

Rapoport reported Monday the Dallas Cowboys had removed themselves from the race to acquire the three-time All-Pro safety but that the Chiefs were still in pursuit. To try to facilitate a move, Seattle had lowered its trade demand from two second-round picks to one second-rounder.

Thomas would've had a major impact on a Kansas City defense that's last in passing yards allowed (362.7 per game) and 29th in opponent passer rating (106.3).

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As good as the Chiefs are offensively, their porous defense could eventually come back to bite them later in the year. They were presented with a unique circumstance in that one of the NFL's best defensive backs remained readily available four weeks into the regular season, and failing to finalize a trade for Thomas could become a "what if" for Kansas City's 2018 campaign.

Thomas is in the final year of his contract with the Seahawks. He sat out the preseason while seeking a long-term deal that would provide him with more financial security.

In a piece for The Players' Tribune, Thomas said Seattle should either honor his request or trade him to a team that would offer him the contract he was seeking.

His injury eliminates any hope of getting a trade this season. Even if Thomas were to return prior to Week 17 or in time for the postseason, Oct. 30 is the NFL's trade deadline. No team will continue going after Thomas with little to no assurances he can play again in 2018.