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SANTA CLARA -- Wide receiver A.J. Jenkins did not take part in the main portion of practice Tuesday after he was seen stretching his hamstring during individual drills.
Jenkins, who did not miss any practices as a rookie due to injury, added to the growing list of receivers who have been out. Kyle Williams missed his second full day of practice. Kassim Osgood also did not practice due to what appeared to be a hamstring strain.
Michael Crabtree and Mario Manningham are on the 49ers' physically-unable-to-perform list.
Jenkins is in competition for a starting job with Crabtree out until at least late in the season. Jenkins, a first-round draft pick in 2012, has yet to distinguish himself on the practice field. Anquan Boldin and Chad Hall had strong days among the 49ers wide receivers.
Center Jonathan Goodwin and linebacker NaVorro Bowman also did not practice Tuesday due to unspecified reasons.