Now Williams is battling a "flare-up" in the same knee after an early exit from Sunday's practice.
"Ryan's going to get a second opinion," Arians said. "We'll see when he comes back. It just flared up. There's no injury; the MRI's clean."
Williams attributed his reduced ability to push off as "just a little irritation." Arians' frustration stems from the fact that Williams looked good in earlier practices before the "surprise" flare-up.
While the clean MRI is encouraging, Williams' injury history and the need for a second opinion suggest the irritation could linger as a setback.
The pressure is mounting on Williams to avoid a lengthy absence now that Arians has acknowledged 2013 as a make-or-break season for the snakebitten running back. After managing just 2.8 yards per carry in five career games through two years, Williams can't afford to enter the season at less than peak form.
UPDATE: Reporter Darren Urban of the Cardinals' official team site tweeted Tuesday that Williams decided not to get a second opinion on his knee and should return to practice Thursday.
RB Ryan Williams ended up not getting second opinion. Feeling better. Should be back at practice Thurs. Team off Wed. #CardsCamp
- Darren Urban (@Cardschatter) July 30, 2013