On a tangential but somewhat related note, I find the psychology of "playing hurt" fascinating. I completely get that players want to gut it out and help their team. That's part of what makes great competitors tick. I remember feeling that way when I played team sports in school. Heck, I did that when I tore a hammie playing ultimate a few years back.
But the question is, when do you cross the line and end up hurting your team by playing when you aren't ready? For example, I think Seahawks fans, Seahawks haters, and everyone in between thought Sherman showed grit by staying in the Green Bay game when his arm looked like it was ready to fall off if it got hit. And I can't figure out for the life of me why the Packers did not go after him. But let's say they had. What if on GB's last drive, Rodgers goes after that side, and Sherman gets burned a few times or misses tackles because of his arm, and GB gets a touchdown and wins instead of a field goal to send it to overtime? Then I think the opinion changes from "look what a gritty player Sherman is" to "he never should have stayed in. After Wilson and the offense brought them back, Sherman cost them the game."
Or to extend that logic over a season, what about Vernon Davis playing for the 49ers? He became a complete non-factor this season. His speed was hampered. He could not get open. He was not aggressive going for balls, and even had some flat-out drops. As a result, his stat-line was that of a sub-par tight end rather than one of the most dominant tight ends in the game, and it (along with other factors) hurt the team this year.
So where do you draw the line? I know this is somewhat rhetorical because there is no simple answer. But I do find it interesting to ponder.