The 30-year-old Bradford is an eight-year pro who was selected by the Rams with the first overall pick in the 2010 NFL Draft.
National Football League teams aren't able to officially sign free agents until Wednesday beginning at 1 p.m. Arizona time.
Arizona is now estimated to have almost $22 million in available cap space, but that's before the expected signing of quarterback Sam Bradford, who will reportedly make $20 million on a one-year deal with an option for 2019.
Bradford's trouble with injuries continued in 2017 as he was limited to just two games because of a third injury to his left knee.
A source told NFL Media's Ian Rapoport Bradford will sign a lucrative one-year contract, which contains an option for a second season. It was reported that the Cardinals were ready to offer Cousins 5-years for $145 million.
The Heisman Trophy victor was drafted by St. Louis with the first overall pick in the 2010 NFL Draft. He's a career 62.5 percent passer with a 1.77 touchdown-to-interception rate. Keenum agreed to a deal with the Broncos, which he's expected to sign Wednesday.
Bradford underwent season-ending knee surgery in November with hopes of curing ligament damage, but the procedure might not have returned him to full fitness. He missed half of the 2013 season and all of 2014 after tearing his ACL in back-to-back years. He was traded to Minnesota in September 2016 and started 15 games that season after Teddy Bridgewater's knee injury.
If Bradford can stay healthy, and that's a BIG if, then maybe he can keep the Cardinals afloat for the next year of two while they get their franchise quarterback ready to go.