Christian Ponder, who started the first three games of the season, will be Cassel's backup, with his fractured rib apparently healthy to allow him to play if needed. Head coach Leslie Frazier said he wasn't sure if newly acquired QB Josh Freeman will be active.
"We don't see him being able to play this ballgame yet, based on where we are and where he is with our offense," Frazier said.
Ponder said Thursday he was disappointed and frustrated with the Vikings' change in direction with the quarterback position.
"I think it's always tough when you make a change at quarterback. You have to take a lot of factors into it when you're doing that," Frazier said Friday. "You don't make those decisions lightly and we didn't. … We'll see how it plays out over time."
Although Frazier indicated the decision has been made for a couple days, Cassel said he was "anticipating" being the starter without "expecting" it.
"It's exciting. That's why you come out here and you compete through (organized team activities) and minicamp and all that stuff," Cassel said. "This week I'll get another opportunity and I'm excited to get back on the field with these guys. Hopefully we can go out there and get another win.
"It's just one more opportunity. Last week we took a great approach and the guys came out and responded well. We all responded well. We played well as a team and hopefully we can build off that. For us, it's always a one-game season right now to get ourselves back in to this race."
Against the Pittsburgh Steeler in London before the Vikings' bye week, Cassel completed 16 of 25 passes for 248 yards, two touchdowns and no interceptions. He completed all 10 of his second-half passes and had a 123.4 passer rating, higher than any in Ponder's previous 29 starts.
Frazier said they would re-evaluated the position after Sunday's game against the Carolina Panthers before deciding on the starter the following week. Cassel said he had enough on his mind concentrating on this week's game rather than thinking about his long-term future.
"To be completely honest, I'm not thinking about any of that stuff right now because once you start concerning yourself with that it takes away from what you have to do on the field," he said. "My sole concern has to be how can we beat Carolina on Sunday and get ready to do that."
Cassel said his reps increased as the week progressed.
Freeman is expected to be the starter once he gets up to speed with the Vikings' offense, but it's unknown if that will happen by their next game against the New York Giants on Oct. 21.
"Probably have to look at some things next week to make that determination," Frazier said. "I'm not sure, even as we speak, if that would be the case. But we'll evaluate it when we come back next week."
Freeman agreed to terms on a one-year contract with the Vikings Sunday night that will pay him $2 million for the remainder of the season.
WALSH COULD BE LIMITED
Pro Bowl kicker Blair Walsh is listed as questionable for Sunday's game after feeling a "twinge" in his hamstring during Thursday's practice.
"We're going to list him as questionable just because of that tightness and not sure how he's going to be," Frazier said. "We need to see some things before the game, but he should be able to go. Just to err on the side of caution, we're going to list him as questionable for the game."
Frazier said Walsh's longer kicks could be limited, but punter Jeff Locke was also an accomplished kicker at UCLA. He will be Walsh's replacement if needed and the Vikings have a short list of kickers they could sign if they know Walsh can't play before Sunday, which isn't expected to be the case.
Tim Yotter is the publisher of Viking Update. Follow Viking Update on Twitter and discuss this topic on our message boards. To become a subscriber to the Viking Update web site or magazine, click here.