An MRI exam on quarterback Tony Romo's back did not offer good news for the Dallas Cowboys on Monday: He has a herniated disk that could require surgery, according to a source.

The Cowboys, even while refusing to rule out Romo for Sunday's win-or-go-home game against the Philadelphia Eagles, are making backup plans.

Kyle Orton, whose last start was Jan. 1, 2012, for the Kansas City Chiefs, is the Cowboys' likely starter Sunday. Dallas will sign a veteran quarterback Tuesday, since it has no other quarterbacks on its active or practice rosters. Tyler Thigpen, John Skelton and David Carr will work out at Valley Ranch on Tuesday, a source said.

Coach Jason Garrett wouldn't rule Romo out of Sunday's showdown against the Eagles that will determine the NFC East champion, instead saying Romo would receive treatment each day this week, and the team would evaluate the quarterback's injury each day.

Broncos: Strongside linebacker Von Miller is done for the year after tests revealed a torn anterior cruciate ligament in his right knee, which he injured in the first quarter of Denver's 37-13 win at Houston on Sunday.

Miller's injury ended a rough third season for the Broncos star, which began with a six-game drug suspension and included just five sacks and 33 tackles.

Panthers: Wide receiver Steve Smith is "highly doubtful" for Sunday's game against Atlanta with a left knee sprain, coach Ron Rivera said. However, Rivera said he's optimistic Smith will be ready for the playoffs. Smith had an MRI on Monday that revealed a sprained posterior cruciate ligament.

Saints: Coach Sean Payton said safety Kenny Vaccaro will undergo surgery on a broken left ankle. The injury means the Saints will be without one of their top defensive backs for Sunday's game against Tampa Bay.

Rams: Left tackle Jake Long has a torn ACL and MCL in his right knee, an injury that will keep him out of the season finale against Seattle and require surgery, coach Jeff Fisher said.

Chargers: Coach Mike McCoy refused to divulge any information about Ryan Mathews' injured left ankle but said he expects the running back to play Sunday against Kansas City.

Hernandez trial: A judge may impose a formal gag order in the murder case against former New England Patriots tight end Aaron Hernandez after his attorneys accused the state of allowing leaks they contend could jeopardize his right to a fair trial. Judge Susan Garsh did not immediately rule on the defense's request for a formal gag order.

The Associated Press contributed to this report.