Arians gave himself wiggle room by promising to have a quick hook, which could extend to this week's practices if he doesn't see what he likes.
"I think we need to find out what he can do," Arians said of Thomas, "for the future and the playoffs if it were to come to that. And that's my job to make sure we cover every base."
Arians acknowledged that top quarterback Drew Stanton had a minor setback with his knee sprain last week.
"If Drew were truly healthy, we would start him," Arians said. "But I don't see that happening Sunday."
There is optimism that Stanton will be ready for the playoffs, Arians added, "because he wants to be ready."
Quarterback isn't the only concern on offense. Arians also conceded that Larry Fitzgerald is "nowhere near" the form he showed prior to the No. 1 receiver's own knee sprain. Arians estimated Fitzgerald's health level at "70 percent."
Even with key players banged up, the Cardinals have no plans to rest their starters in the season finale.
"We are playing to win the game," Arians emphasized.