Mathieu's time in Arizona ended after the sides were unable to agree to financial terms.
Per Urban: "[Mathieu]—who had been due a $5 million roster bonus and another $13 million in guarantees on 2018 and 2019 salaries if he remained on the team—was released after he and the team couldn't come to an agreement on a new contract. Mathieu said last week the Cards had asked him to take a pay cut."
It's unclear if the Texans would be willing to pay top dollar for the 25-year-old Mathieu. He would upgrade a pass defense that finished 24th in yards allowed per game (237.4) last season and would add another star to a defense that already includes Watt, Jadeveon Clowney and Whitney Mercilus.