While both Duerson and Seau were star players, the NFL is largely comprised of role players with very little guaranteed money on their contracts. Essentially, they can be cut at any time and no longer have any source of income. It seems that this is what drives players to continue to play through their concussions or other injuries. If they are seen to be injury prone, or specifically concussion prone, they may not be signed again when their contract expires. Such was the case with perennial Pro Bowl receiver Wes Welker, who was blacklisted by nearly every NFL team after repeatedly suffering from concussions throughout his ten-year NFL career.