Lawyers acting on behalf of an NFL player and gay rights advocate who accused his former coach of being a “bigot” for making homophobic remarks have said they have text messages to back up the allegation.

Chris Kluwe, a former punter for the Minnesota Vikings, earlier in January published an article on Deadspin, in which he said he was “pretty confident” that his sacking came off the back of his equal marriage support, and which accused one of his coaches of making homophobic remarks.

“If there’s one thing I hope to achieve from sharing this story, it’s to make sure that Mike Priefer never holds a coaching position again in the NFL, and ideally never coaches at any level,” Kluwe wrote in the article.

He later said he “may have been a little too harsh” in calling for him to be sacked, and said that he hoped Priefer could make “legitimate change” in his stance on gay rights.

Acting on Kluwe’s behalf, lawyer Clayton Halunen told the Pioneer Press that there were text messages from a witness to the remarks, Blair Walsh, a kicker for the Vikings.

The owners of the Vikings on Saturday released a statement saying: “Vikings ownership was entirely unaware of Chris Kluwe’s allegations prior to the Deadspin article earlier this month.”

The revelation came at the weekend during a five-hour meeting with investigators, during which Halunen also said that Kluwe would be willing to take a polygraph test.

In a statement given on 2 January through the team, Walsh defended Priefer, saying Kluwe’s accusations were “totally not compatible with what Priefer stands for”, but did not categorically deny that he made the statements.

Halunen said Kluwe still had a record of a text message sent by Walsh in reference to a statement by Priefer, during which he allegedly said: “We should round up all the gays, send them to an island, and then nuke it until it glows.”

“If Walsh is going to lie, this will all be exposed, I’m confident,” Halunen said. “If Walsh is going to lie, that’s his choice. But at the end of the day, we believe this is going to come out. We have evidence. So he made that choice, I guess.”