LONDON -- Christian Ponder did not take part in practice Friday, which means Matt Cassel will start Sunday's game against the Pittsburgh Steelers.

The Vikings' Twitter feed reported at 6:40 a.m. that Cassel will get the start at Wembley Stadium.

Coach Leslie Frazier said at his press conference Friday that Ponder has a fractured rib, and there is no timetable for his return.

Ponder said this morning the play where he got hurt happened early in the second quarter of last Sunday's game against Cleveland.

Ponder was on the field but not participating with teammates during the portion of practice that is open to media. Ponder had a CT scan on Monday, Frazier said, and the team feels it is too risky for him to play Sunday.

Ponder, who suffered a rib injury in the loss to the Browns, said he made progress Thursday but acknowledged that his status would be determined after consulting with Frazier and head athletic trainer Eric Sugarman.

His injury opens the door for Cassel, who signed with the Vikings this offseason. Cassel has started 62 games in his 9-year career. Frazier was asked Thursday what the team liked about Cassel before signing him.

"The fact that he had had success as a starter, leading Kansas City to the playoffs [in 2010]," Frazier said. "[He] played behind a future Hall of Fame quarterback in New England so he understood what it means to prepare as a backup. All those factors – his success in the league as a backup and starter – along with his experience were ingredients that we thought would help us. His resume was impressive and he's been just as impressive watching him in practice and meeting rooms as well."

We'll be back in a while with updates fronm Frazier and hopefully Ponder and Cassel.