New England Patriots star quarterback Tom Brady left the practice field with an apparent injury to his left knee, the same knee that cost him his season five years ago with a torn anterior cruciate ligament.
A fan posted a video via Twitter that shows Brady go down and clutch his knee.
This injury may not be that severe, though.
Several reporters said Brady grabbed his knee after an incomplete throw without being hit, limping off the field before going back on the field to continue. Then, Brady jogged off and went to get checked out after talking with Patriots coach coach Bill Belichick, offensive coordinator Josh McDaniels and head trainer Jim Whalen.
It's unclear what the nature of this injury is, but obviously it's a concern for the Patriots.
If Brady is sidelined, their new starter would be Ryan Mallett and the backup would be Tim Tebow.
Stay tuned for further developments.
Follow me on Twitter: @RavensInsider
Aaron Wilson covers the Ravens for The Baltimore Sun.
Check out our partners at TiqIQ for the best deals on all games on the 2014 NFL schedule.
SEP 12 Football Rumor Mill
Here's what you need to know after 2 weeks of college football.
SEP 11 Jesse Lawrence
Jesse Lawrence takes a look at some affordable NFL action this weekend.
SEP 07 Joel Corry
Can the Seahawks repeat? Are the Chiefs and Panthers ripe for a fall? The NFP takes a look at those questions and more.