Frerotte leaves on a cart

Posted by ESPN.com's Kevin Seifert
DETROIT -- The injury to Minnesota quarterback Gus Frerotte is serious enough that he just left the field on a cart.

The injury was announced as a lower back injury. On the last play he was on the field, Frerotte tackled Detroit defensive end Corey Smith after an interception.

Tarvaris Jackson, of course, is the Vikings' backup quarterback.