Professional athletes don’t give in to their fear. They ignore it, rationalize it or pretend it doesn’t exist. Playing scared is a sign of weakness, and the weak get devoured, particularly in the NFL.

It’s startling, then, to hear Cardinals running back Ryan Williams talk so candidly about a play in Arizona’s game against the New England Patriots on Sept. 16.

It was Williams’ second game back after rupturing his right patella tendon and missing his rookie season. Williams had worked diligently to rehabilitate the knee, but he knew it still wasn’t right. He was scared a hit might end his season and threaten his career.

The fear bubbled up inside him the moment he heard quarterback Kevin Kolb announce the play call: 39 Toss.

“That was my least-favorite play, because running to the outside my whole right side was exposed,” Williams said.

He took the toss from Kolb, looked up and saw Patriots linebacker Brandon Spikes closing in. Williams didn’t try to go through Spikes or maneuver around him.

Instead, he gave in — and gave up.

“As soon as I saw Spikes coming to hit me I curled up and forgot about the ball,” Williams said. “It was something where I was trying to protect my leg instead of trying to protect the football. … It’s a scary sight being a running back and being scared to run the ball. That’s something that no running back should feel. I was pretty much scared all last year to get the ball in my hands.”

Williams was so fearful of re-injuring the knee he said it was a “blessing” when he suffered a season-ending shoulder injury against the St. Louis Rams on Oct. 4.

“It’s sad to say, but honestly I was happy because the first thing I thought about was getting my knee right,” he said.

Nearly eight months have passed, and so much has changed around Williams.

The Cardinals have a new coach in Bruce Arians. They got rid of Beanie Wells, signed Rashard Mendenhall and drafted running backs Stepfan Taylor and Andre Ellington.

Williams no longer is viewed as the powerful, athletic running back the Cardinals had such high hopes for when they drafted him in the second round in 2011. He’s the third-year pro who has had two season-ending injuries, played in only five games and has yet to score a touchdown.

Williams won’t dispute the perception change. Nor is he angry the Cardinals drafted two running backs, acknowledging he would have done the same given his inability to prove he can stay on the field.

“I feel like anyone who has been through what I’ve been through is going to be considered damaged goods,” he said.

But Williams has changed as well. Gone are the trademark dreadlocks, replaced by a short haircut that pleased his mother so, “I liked it, too.” More important, he said his knee feels better than it has at any time since the initial injury, thanks in part to clean-up surgery in January that removed, “knots, sutures, drill holes … I got all the stuff taken out and instantly started feeling like myself.

“This is the healthiest I’ve felt in the past two years,” Williams said. “It feels good to be able to run like myself, instinctive and not having to think about what I’m doing, just going out and doing it. I’ve been working real hard, so things are looking good. My stars are aligned this year.”