Williams, a preseason second-team All-SEC selection who led the team in rushing in 2014, suffered a left foot injury Saturday in a Razorbacks scrimmage. A full recovery is expected.
Surgery went well. Blessed— Jonathan Williams (@Jwillpart2) August 18, 2015
Coach Bret Bielema said Sunday that Williams would miss an "extended" period of time. On Monday, Bielema told reporters Williams "won't be with us for the regular season."
"I have no doubt that Jonathan will come back stronger than ever," Bielema said in a statement Sunday. "Anyone that knows Jonathan Williams knows this is just another opportunity for him to prove the man of character and substance that he really is.
"It's an unfortunate injury to a great young man, but we are in the process of gathering as much information as possible," Bielema added. "There are short and long term impacts of how he proceeds, and we want to make sure he does what's best for him and his family and his career beyond Arkansas."
The senior running back played in all 13 games for Arkansas the previous season and started 11. He rushed for 1,190 yards and 12 touchdowns.
Williams was part of the only FBS running back duo of two 1,000-yard rushers; junior Alex Collins rushed for 1,100 yards and 12 touchdowns in 2014. Williams is the school's 10th-leading rusher all-time, with 2,321 yards.
Walker, who can play fullback and running back, excelled in Arkansas' April spring game, with 174 yards rushing and three touchdowns. Rawleigh Williams III was a three-star recruit from Bishop Lynch High School in Dallas.