Rookie Chris Cook is expected to be sidelined for at least two weeks and perhaps longer after suffering a torn meniscus in his right knee Saturday in the Vikings' preseason victory over Seattle, according to NFL sources. That means Cook won't be available for the Vikings' regular-season opener on Sept. 9 at New Orleans.

Cook had a procedure performed on the knee in recent days and an exact timetable on how long he might be out is uncertain.

The injury is a blow for both Cook and the Vikings. The second-round pick from Virginia had been impressive throughout training camp and the preseason and started Saturday's game at right corner after spending the majority of camp playing behind Antoine Winfield on the left side.

Cook had three tackles against the Seahawks and made a couple of nice open-field tackles as well. That performance made him the leading candidate to win the job opposite Winfield.

Veteran Lito Sheppard likely will get the start in Thursday night's preseason finale against Denver at Mall of America Field at the Metrodome. Sheppard, signed as a free agent in April after one year with the New York Jets, began camp as the starting right corner. Asher Allen then started the second preseason game at San Francisco.

The Vikings now have a potential issue with depth at the corner position after trading Benny Sapp to Miami last week for wide receiver Greg Camarillo. Allen figures to slide into the nickel corner role. The Vikings could keep Sheppard as their starting right corner or look outside the organization for help.

The Vikings also have DeAndre Wright and Marcus Sherels on their roster but they are considered long shots to stick on the 53-man.

The regular-season roster must be decided on by 5 p.m. Saturday.