Per Wade Phillips at his press conference, Newman's groin strain is significant and he will be out a while. The good news is that an MRI was negative for structural damage.
From experience I can tell you that a groin strain takes about a week to a week and half to heal where you can start exercising again but it can nag you for a long time after that. I think the Cowboys are really wanting to be careful with Newman and will give him plenty of time to let that groin injury heal so it doesn't bother him any longer than it should.
The only good news I can get out of this is that Mike Jenkins, Adam Jones and Orlando Scandrick will have more opportunities to get some reps and show what they can do. However, if Newman is out for significant time it will really throw a wrench into the Cowboys' sub packages, especially when Anthony Henry takes Roy Williams' spot in the nickel.
Hat tip to Philosopher for the heads up in the comments section.