Ryan Williams walks to the sideline during Sunday's practice; Williams had discarded the ice on his sore knee by the end of the workout.

Bruce Arians was blunt.

The head coach was asked if this was a make-or-break year for running back Ryan Williams: "I would think so."

Williams had been off to a good start, drawing oohs and ahhs at one point during Saturday's practice with a cutback move. But he left Sunday's first padded practice early with a sore right knee, and was planning on getting a second opinion.

"It's just a little irritation," said Williams, who had the knee cleaned out in January. "It's expected with this type of injury I had. I am still kind of dealing with some kinks to work out."

Given Williams’ history, though – he has played just four games in two seasons because of his injuries – any time off the field catches the attention.

Williams started practice Sunday by going through linebacker-versus-running back pass protection drills. He struggled, and soon after, he was wearing ice on the knee. By the end of practice the ice was gone and Williams was able to stand with his teammates to watch.

"He just didn't feel like he could push off," Arians said.

Arians said the initial MRI was clean. Williams said he wants to get a second opinion just as a precaution.

"I'm pretty sure nothing is wrong, but just to make sure," Williams said. "I've been through this once before. I don't want to go through it again."

Williams is still going to have to fight for a job. Veteran Alfonso Smith has looked solid when he has gotten opportunities, and Arians praised draftees Stepfan Taylor and Andre Ellington for their work in the pass-protection drills. Quarterback Carson Palmer noted the race for jobs will come down to the end of camp for the running backs.

Williams knows he still has to prove he can stay healthy. He even said he wasn't sure if he would practice Monday, although Arians said Williams would be sitting out. Williams sees it as a day-to-day situation.

"I've worked hard to not have incidents like this," Williams said. "But it's part of the game."

Williams wasn't the only one banged up Sunday. Guard Daryn Colledge is out for the time being after suffering a nerve problem in his lower right leg. Arians said he didn't have a timetable for a return, but was happy it was not a fracture. Wide receiver LaRon Byrd suffered a concussion, and linebacker Jasper Brinkley has a sore knee.

Linebacker Daryl Washington (neck) will return to practice Monday.