SAN ANTONIO -- Terence Newman's preseason is over.
Newman tweeted: "A little groin pull and be back for the jets! The man upstairs has my back and I have his. Thanks for the encouragement. Have a good night."
Newman had an MRI after practice, which confirmed the diagnosis.
"Initially, (trainers) said through the preseason. They haven't been more specific than that," coach Jason Garrett said Thursday. "So anything else is speculation."
Newman got tangled up with rookie wide receiver Dwayne Harris during team drills and walked off the field with head athletic trainer Jim Maurer.
It is the second time in four seasons that Newman has suffered an injury during training camp that will keep him out of a preseason.
In 2008, he missed four preseason games and the season opener at Cleveland with a groin injury before returning. Eventually he had sports hernia surgery on Oct. 11 of that year and missed five games to recover.
"Terence clearly came back to training camp in great shape. He looked outstanding, really seemed to dive into the defense, understand what his role might be and he was practicing really as well as he's practiced in a long time," Garrett said. "It's disappointing whenever you lose a player of his caliber, but the biggest thing he needs to do is stay engaged with what we're doing on defense and what we're doing throughout our football team and spend a lot of time in that training room to come back as quickly as he can."
Newman wasn't on the field for the team's walkthrough session Thursday morning.
Orlando Scandrick will replace Newman. He has served largely as the Cowboys' nickel corner in his first three seasons.
The injury comes on the heels of the Cowboys missing out on free agent Nnamdi Asomugha, who signed with Philadelphia for five years and $60 million.
Fellow starting cornerback Mike Jenkins sat out 11-on-11 drills Wednesday as a precautionary measure due to a stinger suffered in Monday's practice. Jenkins was in pads and went through individual drills and 7-on-7 drills.
Without Newman and Jenkins, Scandrick and Josh Thomas worked with the first team. On Monday Jenkins said he would be fine but the team does not want to risk further damage.
The Cowboys could get a boost at cornerback on Thursday if the new collective bargaining agreement is ratified in time to allow Alan Ball and Bryan McCann to practice. Ball was last year's starter at free safety but is expected to return to cornerback.
Newman, 32, has been slowed by foot, groin and rib injuries in the past three seasons. He missed three games in 2007 and six in 2008. He needed several painkilling injections but managed to start every game in 2010.
"Terence will be into it mentally. A lot of this is mental gymnastics with everything being new," secondary coach Dave Campo said. "I don't think he'll lose too much there. ... I'm always concerned because he has had a few injuries and again, he's really excited about this season. I really think he will do what it takes to get himself ready and I don't think we're going to play him until he's ready. Hopefully, that will be for the first ballgame."
Todd Archer covers the Cowboys for ESPNDallas.com. Information from The Associated Press was used in this report.