Vikings quarterback Matt Cassel will start on Sunday against the Ravens. Head coach Leslie Frazier said Christian Ponder hasn't passed the concussion protocol. He's still dealing with some symptoms.

"There are some things that, at this stage, [Ponder] has to get done that he wasn't able to get done today," Frazier said of Ponder's concussion tests.

The team will proceed with Josh Freeman as the backup, Frazier said.

Cassel led the team in a 23-20 overtime win over the Bears after Ponder left the game before halftime with the concussion. Cassel went 20-33 for 243 yards with a touchdown and an interception.

"What he did in the second half of that ballgame on Sunday, and also, seeing his comfort level with where we are, and having a comfort level with him, as well," Frazier said of starting Cassel over Freeman. "But his work on Sunday has a lot to do with it. He did an outstanding job in the second half of that ballgame against Chicago."

Cassel said he's approaching this development with a "one-week season" mentality.

"If you start looking ahead, looking for the future, the what-ifs and putting added pressure on yourself, it's as difficult as it can possibly be every Sunsday because there's always good opponents," Cassel said. "But my focus is always on this opponent, this game, and we'll worry about the future later."