(AP Photo/Elaine Thompson)

The Seattle Seahawks are a potential first-round playoff opponent for the Washington Redskins. They would be likely to play at FedEx Field in the opening round of the NFC playoffs if the Redskins beat the Dallas Cowboys on Sunday night to win the NFC East title.

And the Seahawks, already one of the league’s hottest teams, became an even more formidable prospective opponent Thursday when cornerback Richard Sherman won his appeal of his pending four-game suspension for testing positive for a banned performance-enhancing substance. Sherman won’t be suspended and remains eligible to play.

Sherman announced on Twitter that he’d won his appeal. According to reports, he had contended in his appeal that his testing sample had been contaminated because of a broken seal on a cup, breaking the chain of custody in the testing procedure.

A person familiar with the case said Thursday that Sherman’s case in his appeal “was a slam-dunk winner.” The person, who spoke on the condition of anonymity because of the confidentiality of the testing program, said that a “broken chain of custody means everything else doesn’t matter.”