SANTA CLARA -- 49ers defensive tackle Glenn Dorsey might be lost for the season because of a torn left biceps.
The 49ers aren't ruling out Dorsey while they consider options, such as making him their injured reserve/designated-for-return player. Defensive tackle Ray McDonald played much of last season with a partially torn biceps.
The injury to Dorsey, suffered during practice Friday, weakens a defense that already must make due without linebacker NaVorro Bowman (knee) until midseason and might be without Aldon Smith if he is suspended to start the season.
The 49ers' options at nose tackle include Mike Purcell and a handful of linemen who split time at defensive tackle: Tony Jerod-Eddie, Quinton Dial and Demarcus Dobbs, who missed the past few days of practice while tending to a personal mater.
"Tony Jerod-Eddie plays that nose and that end at a very high level as well," coach Jim Harbaugh said, noting how Jerod-Eddie and Dobbs are especially ascending players.
Dorsey was injured less than an hour into Friday's twilight session, perhaps during a goal-line drill. Purcell replaced him on the first-string unit.
Dorsey, who turned 29 on Friday, started last season after Ian Williams suffered a fractured ankle in a Week 2 loss at Seattle. Williams has yet to practice this training camp and is on the physically-unable-to-perform list while he recovers from four surgeries on his left ankle.
McDonald, defensive tackle Justin Smith and cornerback Tramaine Brock did not practice most of last week because of undisclosed injuries.
Dorsey's isn't the first serious injury in camp; No. 2 running back Kendall Hunter suffered a torn anterior cruciate knee ligament in the previous Friday's practice. Dorsey and Hunter are scheduled to become unrestricted free agents after the season.
The 49ers open the exhibition season Thursday at Baltimore. A joint practice Friday has been canceled because of collective-bargaining-agreement rules, though the Ravens will host the 49ers for practices the following three days.