Kurt Warner's agent Mark Bartelstein and the Arizona Cardinals couldn't reach an agreement on a new deal.
Warner will become a free agent at midnight Thursday.
Bartelstein boarded a flight Thursday evening for his home in the Chicago area, but he said he would keep in contact with the Cardinals.
Warner is hoping to land a contract around in the range of the top five quarterbacks in the NFL, $14 million to $16 million a year.
The Cardinals have offered $10 million to $12 million.
Warner, who wants a two-year deal, will likely retire before playing for another team.
Warner, Cardinals Can't Get Deal Done