SANTA CLARA — The 49ers began Wednesday's practice without injured wide receiver Michael Crabtree and apparently nine other potential starters.

Present but not participating in early drills were left guard Mike Iupati, defensive tackle Justin Smith, and linebackers Aldon Smith and Ahmad Brooks. Not seen at the outset were wide receiver Anquan Boldin, center Jonathan Goodwin, left tackle Joe Staley, cornerback Tarell Brown and linebacker NaVorro Bowman.

Crabtree is believed to have torn an Achilles during Tuesday's start of the organized team activities, a source confirmed after an initial report by USA Today. Justin Smith is coming off surgery for a torn triceps, while Iupati and Aldon Smith both reportedly have had offseason shoulder surgery.

Coach Jim Harbaugh is expected to address the media after practice, at about 2:30 p.m.

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