On the Cardinals' official depth chart, Bradford is listed ahead of Josh Rosen and Mike Glennon.
Arizona overhauled its quarterback room following the January retirement of Carson Palmer.
The Cardinals signed Bradford and Glennon when the free-agency period opened in March. Then they traded up to the No. 10 overall pick in the 2018 NFL draft to select Rosen out of UCLA in April.
Head coach Steve Wilks said following the draft the organization still viewed Bradford as the likely starter despite the major investment in Rosen.
"We got Sam to be our starting quarterback, and I would still say that is the case," he told reporters in April. "I'm very excited about Josh ... what he can bring. Every position is open for competition."
Bradford has been a reliable starter since the St. Louis Rams selected him with the first overall pick in the 2010 draft. He's tossed 101 touchdowns and 57 interceptions in 80 career appearances and set the NFL record for completion percentage (71.6) in 2016 before Drew Brees broke it last year.
"Well, right now I'd probably take Sam due to his experience. Due to some of the records that he has in the league," star cornerback Patrick Peterson said in July. "Because when Sam is healthy and is on the field and has talent around him, he's a top-10 quarterback."
He's struggled to stay healthy, however, and missed all but two games in 2017 because of a knee injury.
The durability issues, along with the fact the Cardinals aren't likely to contend, mean Rosen will likely take over under center before season's end. But Bradford will get the call to open the campaign.