AP Sports Writer
TEMPE, Ariz. (AP) -- Four games into the season, the Arizona Cardinals are turning to an undrafted second-year pro to step in at the crucial left tackle position.
Bradley Sowell, claimed off waivers from Indianapolis before the season began, will get the start Sunday against Carolina.
The biggest opportunity of Sowell's career comes after the Cardinals traded starter Levi Brown to the Pittsburgh Steelers on Wednesday for a conditional draft pick.
While Brown was the No. 5 pick overall out of Penn State in 2007, Sowell went undrafted out of Mississippi last year. Initially, he signed with Tampa Bay but was released before the 2012 season began, then signed with Indianapolis.
With the Colts, he drew the attention of Bruce Arians, who moved up from Indianapolis offensive coordinator to interim head coach while Chuck Pagano battled leukemia.
"Excellent young athlete," Arians said, "long, athletic. (He) got stronger and stronger as the year went on, and matured. He even looks bigger and stronger now than when we had him last year."
The 6-foot-7, 315-pound Sowell appeared in 10 games for the Colts and was a backup at both tackles.
Arians and Cardinals general manager Steve Keim said they expect no drop-off from Brown to Sowell.
"Levi was playing so inconsistent that I think Bradley can step in and play at least to that level if not better," Keim said.
Sowell said he "worked really hard" for Arians in Indianapolis.
"In this business you never know when you're going to come back to a coach or how that's going to help you," Sowell said, "and obviously it helped me out a lot with me giving him a lot of great effort last year and this year he's giving me a chance."
Cardinals backup quarterback Drew Stanton was with the Colts last year and said he was impressed with Sowell.
"He was brought here for a reason," Stanton said. "When he became available I knew that was a guy we were going to go out and try and get. I know Goody (Arizona offensive coordinator Harold Goodwin) and BA (Arians) both liked him last year. He was our first guy off the bench as tackle and played in that playoff game last year."
Arizona saves $3.6 million in salary this year by trading Brown, but there are obvious risks in turning to an inexperienced player like Sowell on an offensive line that already was struggling through the first four games of the season.
With a less-than-mobile quarterback in Carson Palmer, the Cardinals can't afford to have pass rushers breaking free.
Asked before Wednesday's practice if he felt ready for the job, Sowell said "as ready as I can be, I imagine."
"I won't know until I get out there obviously," he said, "but all I can do is try my hardest and get out there and see what I've got."
Keim said there would be growing pains.
"We don't expect him to jump in and look like Joe Thomas week one," Keim said, "but what we're banking on is a guy who's going to continually grow and get better and a guy we can win with in the future."
Brown became a lightning rod for criticism of the offensive line's struggles over the years after the Cardinals passed on Adrian Peterson to select the big lineman.
As a rookie, Brown started at right tackle on Arizona's Super Bowl team but after he switched to the left side it became obvious he had trouble with quick pass rushers off the edge.
But he was missed a year ago, when he sat out the entire season with a torn triceps and Arizona stumbled to a 5-11 record, surrendering an NFL-worst 58 sacks.
Arians, replacing the fired Ken Whisenhunt, even called Brown an "elite" tackle.
But Arians' opinion changed through the offseason and training camp. The coach said the Brown he saw in person didn't play like the one he'd seen on tape.
Keim said that Brown "was not living up to our expectations" and that the team had been looking to trade him since the first week of the season.
Nate Potter, a seventh-round draft pick a year ago out of Boise State, will be Sowell's backup.
Notes: The Cardinals placed LB Vic So'oto on injured reserve with a chest injury and signed LB Marcus Benard. ... Arians says it's still "iffy" whether S Rashad Johnson will be able to play Sunday against Carolina. Johnson had the tip of his left middle finger cut off against New Orleans two games ago.
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