Questions at cornerback linger

Earlier in training camp I wrote a column about the Vikings cornerback situation and the unknowns at that position going into the season.

"There are a lot of question marks," coach Leslie Frazier admitted.

While Christian Ponder's development at quarterback remains an overarching theme with this team, the cornerback position is not far behind on the list of concerns as the season approaches.

The Vikings loss to San Francisco on Sunday night highlighted two main issues: Chris Cook's health and Josh Robinson's ability to play the nickel-slot role.

Cook left the game early with a groin injury. Frazier said Tuesday that the injury is not serious, but it was another reminder that the Vikings need Cook to show that he can stay healthy this season as the leader of that group.

Cook has missed more games (22) than he's played in his three seasons. If he can't stay on the field this season, the Vikings are going to put in a bind because they lack depth at that position.

Robinson is listed as the starter at left cornerback but he moves inside to the slot in nickel situations with rookie Xavier Rhodes playing on the outside.

With Winfield gone, Robinson is making the transition to that role -- which he's never played before this season -- and he had a rough performance against the 49ers. He got beat on the first touchdown pass and was in coverage on a number of completed passes.

Vikings defensive coordinator Alan Williams last week praised Robinson's improvement, saying he looks more comfortable in the slot. But opponents almost certainly will test Robinson once the regular season starts.