Crabtree has been missing all season with an Achilles injury, but he carries a big reputation following his role last year when he caught for 1,105 yards and nine touchdowns as the 49ers reached the Super Bowl.
Fisher has said that he has had his men watch tapes from last season so that they know what they are up against.
Fisher told reporters: "We hoped that maybe he'd wait another week. But no, we're expecting him to play.
"So obviously you go back and look before the injury and what he did and we're familiar with that. We have respect for his ability and our young group of defensive backs will certainly be challenged.
"It's hard for us to predict how the 49ers offense and their staff is going to utilize him this week, but we have to be prepared for anything."
The game is a crucial one for Crabtree's team, who sit in third spot in the NFC West as they look to reach the post-season.