Matt Cassel received the majority of first-team snaps during Wednesday's practice. Christian Ponder (ribs) was too sore to take much work Wednesday. The Vikings are hoping he can do more Thursday and insist they don't want to use this injury as a chance to make a quarterback switch. Coach Leslie Frazier said a decision on a starting quarterback for Sunday's game in London will come after Friday's practice. "It's purely circumstantial if that happens," Frazier said of Cassel starting. "We want Christian to play. We want him to get out there and continue to grow and develop as a quarterback."