He understands that backs on the wrong side of 30 are considered the football equivalent of a MySpace page: used up and outdated. Yet here he is at 32, coming off the most productive game of his decade-long career running with a fearless style that proves there is life for the Pittsburgh running game even with All-Pro Le'Veon Bell done for the year with a right knee injury.
''I don't think we can hide him anymore,'' joked guard Ramon Foster.
Blame it on Williams, whose effectiveness is as hard to ignore as the pink-tinted dreadlocks he wears in honor of his mother Sandra Hill, who died in May 2014 following a lengthy battle with breast cancer.
Signed in the offseason following a long run at Carolina - where he is the franchise's all-time leading rusher - Williams was only supposed to be a placeholder while Bell served a two-game suspension to start the season. Williams played brilliantly, running for 204 yards and scoring three touchdowns. Yet he receded into the background without complaint once Bell returned, well aware of the pecking order.
Call it a byproduct of his time with the Panthers, where he spent years as either the one or the two in the one-two punch along with Jonathan Stewart. The system that worked for Carolina, even if it prevented Williams from ever really getting into a rhythm.
That won't be an issue now, with Bell done for the season and newcomers Jordan Todman and Isaiah Pead still getting comfortable with offensive coordinator Todd Haley's playbook. Williams was on the field for 80 of Pittsburgh's 85 offensive snaps, darting for 170 yards against a defense that began the day second in the league against the run.
Williams was even effective when the ball wasn't in his hands, putting together a GIF-worthy block on Oakland defensive end Aldon Smith in which Williams sent the 6-foot-5, 265-pound Smith flying. Not that Williams was in the mood to gloat. While others might consider his play a surprise, he does not.
''I'm not saying this is my best game,'' Williams said. ''The sky's the limit for this team and for myself and for this offense.''
Even if the sky grew a little cloudy in the aftermath of his electric performance. Coach Mike Tomlin said Tuesday that Williams is dealing with foot pain and Williams' availability to practice this week ahead of Sunday's game against Cleveland is in doubt, the price of the back's heaviest workload since lugging it 30 times against Tampa Bay in 2009. It seems unlikely a little swelling would keep him out.
Williams certainly looked fresh on his 27th and final carry versus Oakland, a 9-yard sprint to the sideline that set up Chris Boswell's winning 18-yard field goal. While Williams lacks Bell's patience, he makes up for it with vision and tenacity. He's a brilliant cutback artist who isn't afraid to push the pile forward when he has to.
The key to Williams' success isn't the years, it's the lack of miles. Williams and Reggie Bush are the only backs taken in the 2006 draft - a group that includes Laurence Maroney, LenDale White and Joseph Addai - still in the league. And Williams' 1,522 carries are fewer than LeSean McCoy, Chris Johnson, Marshawn Lynch and Matt Forte, all of whom began the season in their 20s.
It's why Steelers safety Mike Mitchell told anyone in the organization who would listen to take a shot at signing Williams after Carolina let him go in the spring. Williams signed the same afternoon Pittsburgh announced a lengthy extension with quarterback Ben Roethlisberger, the lack of fanfare just fine for a player who keeps a mental checklist of the slights against him.
''It's all about production,'' Williams said. ''I go in and try not to let people out work me ... and it does help when guys like the media doubt me so thanks guys for the fuel.''
Pittsburgh will need Williams' tank to remain full for the Steelers to remain in contention for a wild-card spot.
''He's tough mentally and physically,' Tomlin said. ''He enjoys the drudgery. He loves to come to work. He's a competitor.''
NOTES: Tomlin said there's a slight chance Roethlisberger's injured left foot may be good enough to play on Sunday but the Steelers will prepare as if Landry Jones is starting. ... Tight end Matt Spaeth is out this week with knee inflammation. Linebackers Ryan Shazier (knee) and James Harrison (knee) could be limited in practice.
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