SANTA CLARA Outside linebacker Darius Fleming collapsed Tuesday after twisting his left knee, the second consecutive year he has gone down with an injury to the same knee during the 49ers' spring session.
Last year, he tore his ACL, which knocked the 2012 fifth-round pick out for the season.
This year's injury appears to be only a "tweak," his agent said Tuesday.
After a few frightening moments, Fleming was back on his feet. He watched the rest of the practice and did not participate.
Fleming is one of several young outside linebackers hoping to land a spot on the team. Starters Aldon Smith (shoulder) and Ahmad Brooks (shoulder) have been rehabbing during the spring, and veterans Parys Haralson and Dan Skuta have worked with the first-team defense.
Fleming, fellow second-year player Cam Johnson and third-round draft pick Corey Lemonier are in the backup spots for now. Fleming also has been playing inside linebacker.
Osgood signed One day after bolstering their coverage units with free-agent safety Ray Ventrone, the 49ers signed another special-teams ace, receiver Kassim Osgood. To make room, they cut wide receiver Joe Hastings.
"Every time you watch him, he's first or second running down on kickoffs," coach Jim Harbaugh said of Osgood. "Also does a good job blocking as a wide receiver. Physical player, solid player, and he's part of the competition."
Osgood, 33, is entering his 11th season, and at 6-foot-5 and 220 pounds he's the 49ers' biggest wide receiver. He was with the Detroit Lions last year, but had no starts and no catches.
However, he made the Pro Bowl in 2006, 2007 and 2009 as a special-teams standout, and he adds to a growing list of 49ers' acquisitions with special-teams backgrounds.
The team already has signed free agents Marlon Moore, Skuta and Ventrone to compete for spots on the coverage units. And the 49ers used a sixth-round pick on Nick Moody, an inside linebacker who stood out on special teams in college.
Et cetera Offensive coordinator Greg Roman suffered scratches on the back of his neck when a massive oak tree fell during a lawn bowling outing for 49ers coaches Saturday in San Jose. Two others not affiliated with the 49ers were injured.
Receiver Anquan Boldin tweeted Monday that he would not visit the White House this week with his Super Bowl-winning Baltimore Ravens teammates. However, Boldin wasn't at Tuesday's voluntary practice, either. Harbaugh declined to explain the absence.
Running back LaMichael James joined Frank Gore and Kendall Hunter on a side field with trainers. That made Anthony Dixon, Jewel Hampton and undrafted rookie D.J. Harper the only healthy running backs for Tuesday's practice.
Join The Bee's Matthew Barrows today at 11 a.m. to discuss the 49ers' offseason moves and other news.