Cowboys starting right tackle Marc Colombo fractured his left fibula in the first quarter of Sunday's game here at Lambeau Field.
The injury likely will require surgery, which would probably sideline him at least for the rest of the regular season, according to a Cowboys official.
Third-year tackle Doug Free, a fourth-round pick in 2007, has replaced Colombo against the Packers.
Colombo limped off the field after injuring his leg on the Cowboys' second offensive series. He has started 56 straight games at right tackle since 2006.