AP Source: Tom Brady sprains left knee

New England Patriots quarterback Tom Brady grabs his left knee after an apparent injury during a joint workout with the Tampa Bay Buccaneers at NFL football training camp, in Foxborough, Mass., Wednesday, Aug. 14, 2013. AP

FOXBOROUGH, Massachusetts — A person familiar with the injury says New England Patriots quarterback Tom Brady sprained his left knee in a practice and his return is yet to be determined.

An MRI on the knee confirmed the injury, said the person, who spoke on condition of anonymity because the team hasn’t made an announcement.

The two-time NFL MVP limped off the field Wednesday midway through New England’s joint practice with the Tampa Bay Buccaneers.

Left tackle Nate Solder was pushed into Brady by Tampa Bay defensive end Adrian Clayborn. Brady, entering his 14th NFL season, rocked backward on the ground and held his left knee. He went to the sideline, then returned for a few more plays before talking with coach Bill Belichick and leaving the field under his own power.