Former Raider Carson Palmer is back Sunday night — maybe not for long — and the Cardinals quarterback will surely test Oakland’s highly questioned young cornerbacks in the third preseason game.

TJ Carrie hasn’t gotten thrown at much, because so far St. Louis and Minnesota have had success going after DJ Hayden. The former first-round pick gave up a couple of big plays in the last game Aug. 22, not to mention getting called for a penalty.

Then there’s second-year player Keith McGill, who started training camp ahead of Hayden, but has struggled as well.

Raiders defensive coordinator Ken Norton Jr. said he is not losing any sleep over his young cornerbacks. Not yet, anyway.

“It’s all good until you see them catch the ball,” Norton said. “One of our main objectives is to stay on top — no deep balls. If you don’t see them catching deep balls, then we’re good. So it doesn’t matter whether we’re young or old. Can they play the technique and can they stop the deep ball — that’s what it comes down to.

“The age doesn’t matter. Do they understand the technique, and do they make plays?”

Their window to make plays against a top-notch quarterback like Palmer may be small Sunday night.

Ezra Shaw/Getty Images

There have been a rash of knee injuries around the league this preseason, and Cardinals coach Bruce Arians said he was going to have to look at possibly reducing his starters’ playing time in the third preseason game to play it safe.

It doesn’t look as though Palmer and receivers Larry Fitzgerald and John Brown will play longer than a half.

Raiders coach Jack Del Rio was asked if he was going to have a similar discussion with his staff.

“My thoughts are very similar to Bruce’s,” Del Rio said. “I know we’ve both been in the league a long time, done it a certain way, and there are certain things you kind of expect about what you’re going to do and try to do, but I think you do have to take pause and make sure you think about it. We’ll do that.”

Getting starters a chance to get going after halftime has been the norm in years past.

“You’d like to get the guys to feel coming back in the second half and starting the second half at least,” Del Rio said. “Because that’s what it ends up being that first week of playing with smaller rosters and getting the feel of what it’s like to take that number of snaps in a game. The conditioning aspect, not only physically but mentally, it’s important.

“But you have to weigh that against having your best people healthy and ready to go for the year.”

Dowling cut: The Raiders surprisingly waived safety Jonathan Dowling on Saturday, a day before their third preseason game. Dowling had his first career interception in the Aug. 22 game when he picked off a pass by Minnesota’s Shaun Hill.

League sources say Dowling was cut because of maturity issues and not his play on the field. The Raiders were trying to trade him the past couple of days.

Apparently a series of small incidents built up to the point where the coaches decided to move on; the personalities were a bad fit. Dowling was shocked when he was told.

Dowling had been playing ahead of four-year veteran Brandian Ross this preseason. The Raiders, who start Charles Woodson and Nate Allen at safety, also signed Taylor Mays, who was cut by the Lions, on Wednesday.

It shouldn’t be assumed that Dowling’s departure was tied to Mays’ arrival. Norton, who was on the USC coaching staff when Mays was there, stresses that the sixth-year veteran is just trying to make the team.

“It comes down to competition,” Norton said. “If Taylor wants to be competitive, if he wants to work, if he wants to strain, if he wants to have passion, if he wants to make plays, then this is the place for him. If not, then it’s not the place for him.”

A seventh-round draft pick out of Western Kentucky, Dowling played in seven games last season as a rookie.

The Raiders, currently at 88 players, must trim their roster to 75 by 1 p.m. Tuesday.

Vic Tafur is a San Francisco Chronicle staff writer. E-mail: vtafur@sfchronicle.com Twitter: @VicTafur

Five players to watch

RB Roy Helu Jr.: He is finally back from a hamstring injury and the coaches hope they can relax as the Danville native steps into the third-down role.

RB Trent Richardson: Coach Jack Del Rio said he wants to see some of the explosiveness that Richardson had in college at Alabama. Might need a time machine then.

TE Gabe Holmes: Will the Raiders really keep four tight ends? Holmes had a good training camp but needs to make some noise Sunday.

DT Leon Orr: He’s going to need to make some plays to crack a deep group of interior linemen.

S Brandian Ross: He played well last season, but the new staff had him behind Jonathan Dowling. Dowling was cut Saturday, so Ross has a window to the coaches’ hearts.

— Vic Tafur

Sunday’s game

Who: Raiders vs. Cardinals

Where: Coliseum

When: 5 p.m.

TV: Channel: 11 Channel: 3 Channel: 8

Radio: 98.5