Michael Crabtree could be on the shelf for six weeks, a blow the San Francisco 49ers discovered when the wide receiver showed up.

Crabtree suffered the injury in player-run workouts during June and it’s more serious than anyone anticipated, according to Matt Barrows of the Sacramento Bee. He could potentially miss the entire preseason, something that would no doubt put him far behind in the playbook with the new coaching staff.

Now, the 49ers are in the market for a veteran receiver, per the report, and they made a play for Chad Ochocinco before he was traded to the New England Patriots. They’re currently in discussions regarding Malcom Floyd.

So, Crabtree was placed on the physically unable to perform list along with fullback Bruce Miller and wide receiver Dominique Zeigler. Zeigler is working his way back from a torn ACL. The club has not disclosed Miller’s ailment.

Crabtree had surgery on his foot prior to the 2009 draft. At least he has experience missing preseason. The 49ers are expecting big things from their former first-round draft pick.

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Brad Biggs covers the Bears for the Chicago Tribune