AP

The 49ers could be down to four No. 1 receivers.

Michael Crabtree, a first-round pick in 2009 who has yet to fulfill his potential, potentially could be out for a while with an ankle injury.

Cam Inman of BayAreaNewsGroup.com reports that Crabtree missed Saturday’s practice after injuring the ankle late in Friday’s practice.

Coach Jim Harbaugh would say only that Crabtree is “working through something.” (Maybe he swallowed a Lego.)

“He’ll be all right. He’s good,” 49ers running back Frank Gore said of Crabtree. “He’s going to be ready.”

Crabtree has yet to participate in a full training camp. He held out into the regular season as a rookie, and he has had neck and foot injuries in his other two Augusts.