The 49ers do not consider the injury to be serious, the source said, and Bosa is not expected to miss much time.
With about 45 minutes left in the practice, Bosa appeared to get tangled up with multiple teammates on a running play off the right side and stayed down on the field after the play ended. Members of the Niners medical staff quickly rushed to his side and examined the lower part of his right leg and ankle.
After a few minutes, Bosa was able to stand and walk off the field with two athletic trainers. He slowly headed into Levi's Stadium, without assistance, for further examination.
The No. 2 overall pick in the NFL draft out of Ohio State, Bosa has had a lengthy injury history. He missed most of last season with the Buckeyes because of a core muscle injury suffered in the team's third game. After being drafted in April, Bosa missed most of the 49ers' offseason program with a hamstring issue. He also suffered a torn ACL as a senior in high school.
In this, his first NFL training camp, Bosa had made it through nine practices without issue and was making quite an impression on teammates and coaches. He has worked with the starting defense and the second unit and was with the starters Wednesday before he was injured.
"He's been progressing very well; very pleased with him," 49ers defensive coordinator Robert Saleh said. "He's got a knack for pass rush, [and] he's been very good in the run game. At this point, he's progressing very well. Overall, we're very excited about him."