UPDATE (2:38 PT Wednesday): 49ers head coach Jim Harbaugh has confirmed that Michael Crabtree has a torn right Achilles tendon.
Crabtree was injured during seven-on-seven drills Tuesday and had successful surgery Wednesday morning. Harbaugh indicated the surgery is not season ending.
UPDATE (1:50 PT Wednesday): Chris Mortensen has tweeted that Michael Crabtree underwent surgery Wednesday. Multiple reports say his timetable for return is roughly six months.
The 49ers' 2013 season took a significant hit on the first day of organized team activities with the reported news that No. 1 receiver Michael Crabtree tore his Achilles on Tuesday.
A USA Today report indicates that Crabtree will soon undergo surgery.
Crabtree, 25, is coming off his best NFL season in which he caught 85 passes for 1,105 yards and nine touchdowns -- all career highs. The 49ers made him the 10th overall selection in the 2009 NFL Draft with their first pick.
San Francisco acquired wide receiver Anquan Boldin from the Ravens for a sixth-round draft pick, and may need to go outside the organization to fill the void left by Crabtree.
[REWIND: 49ers acquire Boldin from Ravens]
Youngsters A.J. Jenkins, Ricardo Lockette and Quinton Patton were expected to compete for the No. 3 receiver while Mario Manningham and Kyle Williams continue to heal from their respective knee injuries.
Crabtree has a history of offseason issues, including a 71-day hold out his rookie season, and is under contract with the 49ers through the 2014 season.