GLENDALE, Ariz. (AP) Only one rookie is listed as a starter for the Arizona Cardinals for Friday night's preseason opener against Oakland. Brandon Williams will be at cornerback, a position he played for just one college season.

That switch from part-time running back at Texas A&M was the starting point for this rapid ascent to an important role on a team that expects to contend for the Super Bowl.

''I know how hard I worked for it,'' Williams said after practice this week. ''If you work hard for something and you believe in yourself, good things are going to happen.''

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Quarterback Carson Palmer said he's ''just shocked'' at how well the third-round draft pick has performed in training camp.

''He plays as advertised as a physical specimen,'' Palmer said, ''but you just see him get better and get more comfortable. There's not a ton of reps under his belt throughout college and all of that. For a guy to come in to a very complex system and play extremely well, especially for a rookie, I think has shocked a lot of people.''

Coach Bruce Arians said Williams is a better football player than the coach thought he was when the Cardinals drafted him as the 92nd pick overall.

Williams had turned heads when he ran a 4.37 40-yard dash at the NFL Combine, tied for third-fastest among cornerbacks.

''We knew what kind of athlete we were getting but he's a better football player,'' Arians said. ''You never know how mature a guy is going to be when you draft him. He's very, very mature and he's very focused on what he wants to do.''

Williams won the job with Justin Bethel, who started four games last season, on the physically unable to perform list while recovering from foot surgery.

When Bethel returns, he will have to beat out the rookie.

''It's Brandon's job to lose right now,'' Arians said. ''You can't win it not practicing.''

With his long arms, strength and speed, the 6-foot, 200-pound Williams is ''playing very, very well'' against Arizona's standout group of receivers, Arians said.

Williams acknowledged ''it's real tough'' going against the likes of Larry Fitzgerald, Michael Floyd and John Brown.

''I haven't gone against no receivers in the NFL yet,'' Williams said, ''but it's hard to see any receiving corps better than our receiving corps.''

A star running back in high school, Williams originally attended Oklahoma before transferring to Texas A&M, where he found himself in a logjam at the position.

Last year, newly hired defensive coordinator John Chavis looked at Williams as a natural athlete who had the makings of a cornerback, so he and head coach Kevin Sumlin suggested the change. Williams readily agreed.

A year later, Williams is an NFL training camp standout.

He gives much of the credit to help from All-Pro cornerback Patrick Peterson.

''On the field, off the field, technique, just everything,'' he said. ''He's really been my mentor, a big brother, everything I could ask for. Throughout this process, he's been there for me.''

Whoever plays cornerback opposite Peterson will see plenty of action. Teams are reluctant to throw in the All-Pro's direction.

Williams knows that full well but believes he can do the job.

''To me, it's just football, man,'' he said, ''knowing what you need to do, knowing you've got somebody to back you up, knowing you've got teammates like Pat, knowing you've got coaches like (cornerback coach) Kevin Ross. Going into it, thinking about the whole situation, I feel like I'm ready.''

Williams gets his first big test against the Raiders. Arians said the rookie will play longer than the other starters in Friday night's game just to get more experience.

Arians usually likes to bring rookies along slowly.

''He will be an exception,'' the coach said.

Notes: Arians said that Earl Watford (bruised knee), the backup player all along the offensive line, will be one of 10 players to miss the Raiders game due to injuries. Others include wide receiver John Brown (concussion), defensive tackle Corey Peters (plantar fasciitis) and defensive lineman Robert Nkemdiche (high ankle sprain), the first-round draft pick who has yet to practice due to his injury. ... Arians said Palmer will play 10 to 12 plays and backup Drew Stanton will see ''a little bit.'' Matt Barkley will be the quarterback most of the game, with rookie Jake Locker taking over in the fourth quarter.

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