Trent Williams wants to play into his 40s, vowing not to retire "with some left in the tank"

49ers left tackle Trent Williams was a full participant in Tuesdayâ??s mandatory minicamp.Williams soon turns 37, but he is still going strong as he prepares for his sixth season in San Francisco."I just feel like I do myself and my teammates a disservice if Iâ??m looking toward the end," Williams said, via David Bonilla of 49erswebzone.com. "Iâ??m paid. People count on me to be here now. Weâ??ve got goals and aspirations as a team. I just donâ??t think putting brain power toward that helps us get to where we want to go."When it happens, it happens. I think, one day, coming in, I should know when itâ??s getting that time, and then, I do the responsible thing and let them know early enough so that they can make the adjustments needed."Williams doesnâ??t yet know when the end will be, but he does know he wants to play into his 40s."I would love to make it into that special group, but if itâ??s not in my cards, itâ??s not in my cards," he...