Can I just say that a lot of people have torn their ACL and still function? Flacco is definitely a tough dude, but a lot of people can cope without having an ACL. Also, if it's a full tear, then they aren't excruciatingly painful. He probably felt a pop, had a little pain, and maybe a little instability. My friend tore his ACL in highschool and still plays basketball with us every weekend. He's 33 now. Now if you're a pro athlete then they will always repair it because you will be less stable and therefore at a higher risk of injury.