"The foot injury that kept Michael Crabtree out of player-run practices in June is more serious than previously believed, and the 49ers' top wide receiver will miss as many as six weeks of training camp and the preseason, according to a source with knowledge of the injury.

That's why the 49ers were in the running this week for veteran wide receiver Chad Ochocinco, who instead was traded Thursday from Cincinnati to New England. The 49ers will continue to pursue a veteran receiver on the free-agent market who could start opposite Josh Morgan when the season begins. They are one of several teams pursuing free agent Malcom Floyd (River City High School).

The nature of the injury is not known. The 49ers will place Crabtree on the physically unable to perform list with rookie fullback Bruce Miller and veteran wideout Dominique Zeigler to begin training camp.

Zeigler is recovering from an ACL tear suffered last season. Miller's injury is not known.

Players who begin training camp on the PUP list can be moved to the active roster at any time. If a player begins the regular season on the PUP list, however, must sit out his team's first six games.

Crabtree, who had surgery to correct a stress fracture in his left foot in early 2009, reinjured it June 6, the first day of a player-run minicamp. At the time, Morgan said Crabtree was sore from wearing new cleats on San Jose State's artificial field.

Crabtree attended the classroom portions of the next three sessions but did not join teammates for practice. When the offensive players assembled again at the end of the month, Crabtree went through warmups with his teammates but did not participate in full practices. Crabtree avoided the media after those sessions, riding in a golf cart to a parking lot and then getting in his car."