''I truly have not made up my mind yet,'' Shell said. ''We're still in evaluation (and) we're looking at it. They both are doing good.''
Walter, who has started the past seven games after Brooks was injured in Week Two with a strained pectoral muscle, has passed for just 1,305 yards and three touchdowns while being intercepted nine times and sacked 40 times. He's also the lowest-rated quarterback in the NFL at 54.6.
Brooks wasn't doing much better before getting injured against Baltimore. In a little less than five quarters, the 30-year-old failed to throw a touchdown or an interception while getting sacked seven times.
Brooks was hurt trying to recover a botched snap against the Ravens on Spet. 17. Since then he's faced a slow recovery that wasn't completed until this week when Brooks deemed himself fit and ready to return to the lineup.
Shell, who was miffed at Walter for comments the young quarterback made following Oakland's 17-13 loss to Denver last week, has been encouraged by Brooks' progress the past two weeks but held off on announcing who the Raiders' starting quarterback will be.
''I'll get input from the staff and stuff like that to see where we are,'' Shell said. ''Andrew could easily be the starter on Sunday.'' Oakland might also get injured offensive linemen Robert Gallery and Jake Grove back in the lineup. Both practiced Thursday and appear closer to returning to the lineup.
''They both worked two days in a row now so that's been good for us,'' Shell said. ''Those guys seem to be OK. We have a couple more days to get through some work and get rested, so we'll see how it goes. If they're ready to go, they'll go.''