Which is why his short list of running backs who have left a lasting, physical impact on him consists of two: future Hall of Famer Adrian Peterson and 49ers rookie Elijah Mitchell. That Peterson, who accidentally decleated Williams when he was a freshman at the University of Oklahoma, is one of those names is no surprise.
That Mitchell, listed at 5-foot-10, 200 pounds, is the other, probably is.
"Elijah didn't decleat me but he definitely put one in my back and it made me turn around like, 'Who the hell was that?'" Williams said. "I was like, 'Damn, that's what they feel when they've got to tackle him?' I can tell why he breaks so many tackles."
Williams' reaction to colliding with Mitchell in the first quarter of an Oct. 31 win against the Chicago Bears undoubtedly echoes the sentiments of opposing defenders. They likely had little idea who Mitchell was before the season but are now well aware of the Niners' latest prized runner.
It's no coincidence the 49ers' three-game winning streak has coincided with a resurgence in their running game. During that stretch, the Niners have their highest rushing yardage totals of the season -- 156, 171 and 208, for an average of 178 per game, up from the 113 they averaged during the first eight games. That physical dominance has allowed the Niners to become the first team since the 2018-19 Baltimore Ravens to average 37-plus minutes of possession in three straight games.
Despite missing the Jacksonville game on Nov. 21 because of a fractured finger, it's Mitchell who has been at the center of it all, offering a mix of expected speed and surprising power even when playing through a variety of injuries.
"I just feel like Elijah is an all-around back," receiver Deebo Samuel said. "He can play like he's 240 pounds and he runs like 190 pounds. You've got the speed, he's got the physicality and he's got the mindset. He's just a great overall back."
Indeed, Mitchell is mounting a case as the most successful rookie running back in franchise history. Through 11 games, he is 10th in the NFL in rushing yards (693), third in rushing yards per game (86.6) and ninth in yards per carry among running backs (4.85). Despite playing in just eight games, Mitchell has 100-plus yards in half of them, surpassing Billy Kilmer for the most such performances by a rookie in franchise history.
A rookie or unheralded back making an impact has become commonplace around the 49ers and other Kyle Shanahan-coached teams for more than two decades. While the easy assumption was that third-round pick Trey Sermon out of Ohio State would be the one to do it this year, it was Mitchell, taken in the sixth round out of the University of Louisiana, who made an early impression on Shanahan and his staff, earning him the starting job after veteran Raheem Mostert was lost for the season to a knee injury.
Mitchell ran a 4.33 40-yard dash at his pro day, but Shanahan said he could see early glimpses that Mitchell was more than just a speed burner. During the early days of training camp, Shanahan and offensive coordinator Mike McDaniel noticed Mitchell's ability to see the whole field, make quick, emphatic decisions and hit the hole at full speed.
"There's some stuff to his game that the more he plays, the more you realize that he's a special young player and there's a reason why he's having productivity," McDaniel said. "You'd have no way of knowing. Even grainy Louisiana-Lafayette tape wouldn't tell you that."
What wasn't necessarily expected was Mitchell's level of physicality. One thing Shanahan and his coaching staff harp on is what linebacker Fred Warner calls "leaky yards," which are those extra gains that come after a runner has seemingly had his progress stopped.
On multiple occasions this year, Shanahan has called a run for Mitchell, watched him get stacked up by defenders and turned to his play sheet for his next call thinking it was second-and-10, only to be told by assistant coaches on the headset that isn't the case.
"I start to look down and think about what I'm calling next and then people in the box tell me it's second-and-6," Shanahan said. "I don't totally believe them because I saw that he was going down and I don't realize that he fell forward and got four yards. When it's like that, which he does all the time now, you keep going, it helps you keep doing it."
Indeed, Mitchell is establishing himself as a different kind of YAC Bro. According to Pro Football Focus, Mitchell is averaging 3.84 yards per carry after first contact, which is second in the NFL and a strong complement to the yards after catch provided by the likes of Samuel, receiver Brandon Aiyuk and tight end George Kittle.
According to Shanahan, that innate ability is as much a mental gift as a physical one. Which begs the question: Where does it come from?
Mitchell was a two-star recruit coming out of Erath (Louisiana) High and injuries during his senior season left him with few scholarship offers. He entered the NFL in similar fashion as a relative unknown with little in the way of outside expectations.
But those slights, whether real or perceived, are now felt by defenders -- and occasionally his teammates -- any time Mitchell touches the ball.
"It's just a different mindset on the field," Mitchell said. "Whoever's in my way, I just try to run the ball and run over him. If anything, I run by him. So it's just a mindset that I have and I'm going to continue to have that."