Cardinals cornerback Justin Bethel (28) is congratulated by safety Tyrann Mathieu Sunday after Bethel returned an interception for a touchdown.

Justin Bethel waited. And waited.

The Cardinals' third cornerback was in a defensive package or two for the first two games of the season, but he was never tapped on the shoulder to get on the field. That didn't come until Week 3, when Bethel went out on 3rd-and-10 on the 49ers' first possession and promptly intercepted San Francisco quarterback Colin Kaepernick.

Bethel returned the pick – his first in the NFL -- for a touchdown. The Pro Bowl special teamer went on to get 10 more defensive snaps the rest of the 47-7 rout over the NFC West rival.

On a team that has been excellent defensively – the Cardinals have allowed 49 points, tied for third in the NFL – regular work

can be hard to come by for some. Big play aside, Bethel understands.

"When it comes to getting defensive reps, when your time comes and your number is called, you have to go out there and make the plays," Bethel said Monday. "You go and train every day, know what my role is for the week, and try and execute it."

Getting on the field isn't simple. Bethel has just 11 defensive snaps, stuck behind a group of defensive backs that are the backbone of the defense – five corners/safeties are among the seven defensive players who have played at least 80 percent of the defensive snaps, and the sixth, Tony Jefferson, was there before Sunday.

Kevin Minter has become a revelation at inside linebacker and Deone Bucannon plays his safety-as-linebacker role. Both Bucannon and Minter have been 80 percenters. That leaves Sean Weatherspoon, a key free agent signing, fighting for snaps. Weatherspoon has 37 in three games.

"We have got a lot of guys like that on defense, who are going to have special roles week to week," defensive coordinator James Bettcher said. "We are going to do our best as coaches and as a defensive staff to put together ways to let those guys go out and do what they do."

It's an attractive amount of depth and this time of year, with the Cards so far sidestepping injuries, it just means more opportunities to mix-and-match. There's a reason coach Bruce Arians likes to talk about having 16 starters on defense.

"I was always taught when you are on the field, you are a starter," said defensive end Cory Redding, one of a seven-man defensive line rotation that has only two players – Calais Campbell at 128 and Frostee Rucker at 110 – to play more than 89 snaps.

"We know who our starters are, we know who our five-star guys are, we know who our playmakers are," Redding said of the multi-layered depth chart. "We let our playmakers do what they do, and when we go in the game, we make sure the level of play doesn't go down."

At some point, injuries will occur. In Bethel's case, the Cardinals only have two other cornerbacks on the roster, and if something happens to Patrick Peterson or Jerraud Powers, his defensive responsibilities will certainly skyrocket.

Until then, Bethel will try and maximize what he gets. It may not turn out to be an interception every time, but another pick or two probably wouldn't hurt his case to get more defensive snaps.

"When you have the depth that we have," Arians said, "we try to keep roles for everybody."

EXTRA POINTS

Arians said running back Andre Ellington and guard Mike Iupati, both dealing with knee injuries, will be limited to start practice this week. They both have a chance to play Sunday against the Rams. …

Arians said right tackle Bobby Massie was solid, and was beaten on one play because of crowd noise, forcing the Cardinals to use a silent count at home – something that doesn't please Arians.

"Wish it wouldn't happen right now," Arians said. "We would hope that the visiting team wouldn't get that many tickets and have to use a silent count at home."