FRISCO, Texas -- Dallas Cowboys quarterback Tony Romo suffered a broken bone in his back during Thursday's preseason game, and a source confirmed to ESPN on Saturday that he could miss six to 10 weeks.
The source told ESPN that the injury -- suffered on the third play against the Seattle Seahawks -- is a compression fracture of the L1 vertebra. A source also told ESPN NFL Insider Ed Werder that Romo would not require surgery.
Coach Jason Garrett said the injury will not cost Romo the season and declined to rule out the quarterback for the regular-season opener against the New York Giants on Sept. 11.
"We don't believe that to be the case at all," Garrett said on a conference call when asked if Romo's season is in jeopardy.
CBS Sports first reported that Romo could miss up to 10 weeks.
Romo first learned of the MRI results on his back Friday night. If he cannot play Week 1, rookie fourth-round pick Dak Prescott is expected to start against the Giants.
Cowboys executive vice president Stephen Jones said he spoke with Romo many times over the past two days.
"He's driven for this not to be like last year," Jones said. "He's certainly not deterred, and he really feels like it's going to be different, but he can get through this, and he also feels very confident that our team can win football games without him while he's not here. He's driven to help Dak win football games for us so that when he gets back we have a great chance to have a great season, get in the tournament and contend for a championship. Nothing's changed."
The injury affected the Cowboys' outlook in Las Vegas, where the team's odds to win the Super Bowl shifted from 16-1 to 20-1 at the Westgate Las Vegas SuperBook.
Garrett said the injury is not related to the surgeries Romo had in 2013. The coach would not say if it is the transverse process fractures Romo suffered in 2014 that forced him to miss a game.
"It's not related to the other back issues that he's had [and is] very specific to the hit he took the other night at the game," Garrett said. "And he came out and he was lobbying to go back in. We decided to not have him go back in, and then he actually felt fine after the game. Then he woke up on Friday morning and didn't feel so good and [the back] stiffened up on him, and that's when we did the MRI. And that's what we found."
Romo was hit from behind by Seahawks defensive end Cliff Avril while scrambling upfield Thursday. Romo immediately reached for his lower back but was able to walk off the field under his own power. He lobbied to return to the game, but Garrett went with Prescott.
This could be the fourth straight year that Romo misses at least one game. He missed the 2013 season finale after undergoing a discectomy. He missed one game in 2014 with two transverse process fractures in his back and was out 12 games last year with a twice-broken left collarbone.
A source close to Romo told Werder that the quarterback isn't considering retirement and there is no doubt that he will play this season.
Center Travis Frederick said the team was surprised by the news on Romo when it reported to its new practice facility Saturday.
"Still trying to take it in a little bit," Frederick said. "The name of the game for us has always been focusing on taking things one day at a time and also have the 'next man in' mentality. Being able to have Dak step up and be able to take over that role and just support him in any way that we can."
Prescott was elevated to the backup job when incumbent Kellen Moore broke his right ankle in a training camp practice.
The former Mississippi State standout has a preseason passer rating of 137.8, completing 39 of 50 passes for 454 yards with five touchdowns and zero interceptions. He also has two rushing touchdowns.
"Dak has done a nice job really at every turn starting back at training camp," Garrett said. "I thought he did a particularly good job in this game against Seattle because he certainly didn't anticipate going in on the fourth play of the game."
ESPN staff writer Ben Fawkes and The Associated Press contributed to this report.