Chris Mortensen explains how Earl Thomas' missing practice twice this week has the Seattle Seahawks considering a significant fine for the safety. (0:59)

The Seattle Seahawks are considering levying a significant fine on safety Earl Thomas for conduct detrimental to the team because he missed practice twice this past week, according to organizational sources.

No final decision has been made yet on the fine, sources added. Thomas did participate in Saturday's walk-through and plans to play Sunday against the Dallas Cowboys. Seahawks coach Pete Carroll said Saturday evening that he plans to start and play Thomas.

The Seahawks have engaged in trade talks with teams, including the Cowboys, about Thomas, but the Kansas City Chiefs have emerged as a candidate if a deal is made before the Oct. 30 trade deadline, sources said. Thomas sat out training camp and also irritated the Seahawks when he appealed personally to Cowboys coach Jason Garrett to trade for him after a Week 16 game in Dallas in 2017.

One league source told ESPN's Adam Schefter that a trade sending Thomas to Dallas is "a super-long shot." Seattle already has turned down a second-round draft pick from the Cowboys, and wanted more for Thomas.

Some sources around the league believed that the Seahawks did not want to trade Thomas until after they played the Cowboys in their home opener Sunday.

Thomas' unhappiness and this week's absences have led the Seahawks to take a hard-line stance against negotiating an extension or any adjustment in salary, sources said. Thomas makes $8.5 million this season, the final year of a four-year, $40 million contract.

The Seahawks' position is that Thomas was rewarded handsomely on a second contract and they have prioritized signing defensive end Frank Clark and receiver Tyler Lockett before they would take Thomas into consideration based on their salary-cap and roster management, sources said.

Thomas was at practice Friday but did not take part because of reasons of a personal nature, according to Carroll, who confirmed that his absence had nothing to do with an injury.

The Seahawks already are 0-2 in a season where they are remaking, if not rebuilding, their roster. If they continue to lose, it would make sense for the Seahawks to try to recoup in a trade more than the 2020 potential third-round compensatory pick they could get if Thomas left as a free agent after this season.

Houston played in Seattle last season and then traded offensive tackle Duane Brown to the Seahawks the day after the game for second- and third-round picks. But it's unlikely that the same scenario repeats itself this season, with Thomas, 29, being dealt to Dallas the day after playing a game in Seattle.

Thomas held out from all offseason work with the Seahawks in hopes of getting a new contract. The move did not succeed, and he reported to the team before the start of the regular season.

Thomas made it clear upon his return, however, that all was not forgiven -- at least not on his end. He wrote in an Instagram post that the "disrespect has been well noted and will not be forgotten."

ESPN's Adam Schefter, ESPN's Brady Henderson and The Associated Press contributed to this report.