Oakland has a bye this week and don't play again until hosting Cleveland on Oct. 1.
''It means that it's anywhere from 2-4 weeks,'' Shell said. ''That's where we are with that.''
With Brooks out, backup Andrew Walter will take over the reigns of Oakland's offense. Walter replaced Brooks in the 28-6 loss to Baltimore on Sunday and had a rough go of things, completing 10 of 27 passes for 162 yards. He was intercepted three times, sacked six times and fumbled three times, losing one.
''He did some good things and some things he could have done better,'' Shell said of Walter. ''There were a couple of situations where the decision-making could have been a little bit better, as far as making the right decisions, where to go with the ball. And again, he had some pressure and that's something that he had to deal with and something we have to try to make sure we try to take care of this week as we evaluate what we've been doing and how we've been doing it.''
Shell said the Raiders would spend the bye week trying to correct their problems up front. Oakland quarterbacks have been sacked 15 times in two games, putting them on pace to shatter the NFL record for most sacks surrendered in a single season.
The team began addressing their problems Sunday when rookie right guard Paul McQuistan was benched in the second half in favor of fellow rookie Kevin Boothe. Shell said the team is open to making other changes, as well.
''That's always possible,'' Shell said. ''We'll look at every aspect of it and if there's something that we can do to make the group better then we'll do that.
''We're going to evaluate everything that we've done for the last couple of weeks, as far as scheme, as far as how we're using our protections, help as far as protections are concerned, and see what we can do to come up with an answer to try to help the guys up front. At the same time we have to continue to work with them individually and make them better.''
The Raiders also need the bye to get healthy. Left guard Barry Sims has a hip injury that has the coaching staff concerned. He was being taken for an MRI test on Monday but the results were not immediately available.
Linebackers Grant Irons (lower back) and Kirk Morrison (bruised ribs), and cornerback Fabian Washington (hamstring) were also hurt in the loss to Baltimore and join an injury list that already included cornerback Nnamdi Asomugha and linebacker Sam Williams.
The Raiders will practice Tuesday, Wednesday and Thursday before getting a three-day mini-vacation. They return to practice next Monday to begin preparing for Cleveland.