Frerotte was listed as doubtful after Friday's practice. Coach Brad Childress said Frerotte is improving, but "it's not a leaps and bounds thing."

Frerotte suffered a lower-back injury late in the first half last Sunday in the Vikings' 20-16 victory at Detroit. Jackson, who was benched as the team's starter after the first two games, replaced Frerotte and led the Vikings back from a 6-3 halftime deficit.

While the Vikings have yet to reveal any further information about Frerotte's injury, he reportedly suffered a broken bone in his back that will sideline him for one or two weeks.

The Vikings likely won't announce the starter until game day, but that isn't surprising considering Childress has tried to keep everyone, including his opponent, in the dark before on such issues.

"I wouldn't say it's official yet," Vikings offensive coordinator Darrell Bevell said midweek. "Gus came in feeling better today and he's making a push to still try and make it. We think he has the ability as a veteran to do it on fewer reps so he's going to make a push and in the meantime that he's not out there, Tarvaris will continue to go."

Jackson completed eight of 10 passes for 105 yards with a touchdown and a 143.8 passer rating.

Sunday's game will mark the Vikings' final regular-season road game this year. They will close by playing host to the Falcons and New York Giants.

SERIES HISTORY: 19th regular-season meeting. Series is tied, 9-9, but Vikings have won two playoff games between the teams. The Vikings beat the Cardinals, 31-26, in the last meeting on Nov. 26, 2006 at the Metrodome.