WESTFIELD -- The Colts' first-team defense saw its first extended look against another team on Wednesday, when the Cardinals came to town for the first of two joint practices.

The result was the extreme version of what we've seen this training camp:

The pass rush dominated.

And the secondary got annihilated.

Kyler Murray finished 6 of 8 in the 11-on-11 portion of practice. He had a couple attempts swallowed by sacks by Laiatu Latu, DeForest Buckner and E.J. Speed.

Murray was constantly on the move, as Buckner and Latu looked unblockable at times, with Kwity Paye adding more of a steady presence on the other side.

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Murray's elite scrambling allowed him to get free sometimes, and when he did, mostly bad things happened for the Colts defense. He completed a deep flag route for more than 40 yards to Chris Moore on a play where Julian Blackmon had to come screaming over to the left sideline from his deep middle safety spot to cover up for a bust by JuJu Brents.

This was Brents' toughest day yet, as he often saw matchups other than Marvin Harrison Jr. and struggled to stay with opponents down the sideline or across the field. The second-year cornerback has had a strong training camp when he's been healthy, but he missed Friday's practice and Sunday's preseason game to rest a shoulder issue, and it's fair to wonder if he's completely healthy right now. He did not look comfortable on many of Wednesday's reps.

The Colts seemed to build their coverage plan around handling Harrison, the No. 4 pick in this year's draft and the son of the Colts Hall-of-Fame receiver with the same name. They didn't travel with him, allowing either Jaylon Jones or Kenny Moore II to handle most of the reps based on whether he was in the slot or out wide. But they often had Nick Cross shadowing him in addition to those two, and it limited most of Harrison's catches to short crossers.

Harrison did beat Cross and Jones on a deep comeback route, where Jones tried to guard against his speed deep but gave up enough cushion to let Harrison catch and run.

The problem is it put the other cornerbacks in 1-on-1 situations, and the Cardinals were able to generate free releases against their press tendencies with a heavy use of motion. That allowed names such as Moore, Michael Wilson and Trey McBride to have productive days. That visual became more clear in 7-on-7 settings, when the Colts pass rush was off the field, and their cornerbacks struggled to stay close in coverage.

That was true for the first and second teams, as Dallis Flowers and Jaylon Simpson also got beat multiple times for chunk plays. Flowers did make up for it some with an interception on Clayton Tune in 11-on-11, when he jumped a hitch route and had a chance to take it to the house.

Perhaps no play summed up the day more than one of the final 11-on-11 snaps, when Latu beat the tackle so easily that he cut off Murray's scramble before he could even get into it for an easy sack, only for the secondary to be whistled for a holding penalty in that short time frame.

"There's obviously some stuff for us to work on," Blackmon said.

Laiatu Latu continues to flash

The Colts were living in the Cardinals' backfield, and the lack of being able to hit the quarterback lowered the upside of what this unit could accomplish. Some of the angles they took on a small quarterback like Murray had potential fumble written all over them.

Two players flashed more than anyone else up front, and they were Buckner and Latu. With an All-Pro like Buckner, that's nothing new. And with Latu, it's getting to the point this training camp where this is the expectation for the first-round rookie as well.

“The way how he just bends, like just seeing him, how he plays – sometimes the tackle will get him on his inside shoulder, and he just takes his shoulder away, drops, bends and just keeps going," Paye said.

"The way he moves is like water."

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The Colts have built their pass defense around this rush, selecting Latu at No. 15 overall to become the final piece to take the group from good last season to elite this year. All the pressure is on him after the loss of Samson Ebukam to a season-ending Achilles tear, but he keeps passing the tests and becoming a menace on passing downs.

Is Julian Blackmon the Colts' second-most indispensable defender?

The Colts had one clear exception to the secondary struggles. (Moore likely fits in this category as well, as the Cardinals didn't target him much.)

Blackmon was the star of the back end once again. He rotated from strong to free safety, mostly playing the latter in 11-on-11 settings in order to help the unit survive the deep ball. He saved a couple of chunk plays from becoming something more by showcasing his speed and pursuit angles to knock players out of bounds.

The highlight came in 7-on-7, when he locked up ex-Colt Zach Pascal on a flag pattern and ran the route for him. Murray slightly overthrew the pass, and Blackmon showed smooth control to turn and find the football and get two feet in bounds.

With the concerns that have mounted with every other safety, plus the leaks in coverage on the outside, Blackmon's ability to communicate and make plays as the strong safety and to be an eraser who still makes the occasional turnover at free safety is remarkable. He's only making $3.7 million this year on a one-year deal, but he looks like Indianapolis' second-most important defender behind Buckner.

The question is whether deploying him in both safety spots is maximizing that value or limiting it. By stretching his versatility, the Colts could spread him thin and take him away from the ball. Can he still make the same impact plays from a single-high look?

“Absolutely," Blackmon said, "You get kind of different route concepts when you're at free and you're looking at different things when you're at strong. So, it's just being able to be versatile in that way could allow me to make many plays."

The Colts can still address the issue if they want to sign All-Pro Justin Simmons, who continues to be available in a depressed safety market. The 30-year-old has 30 career interceptions and has visited the Falcons and the Saints in recent weeks.

Colts injury report

The Colts got a handful of players back on the field. Buckner (rest), Brents (shoulder) and rookie linebacker Jaylon Carlies (hip) were all back after missing varying lengths of time.

Wide receiver Josh Downs (high ankle sprain), wide receiver Ashton Dulin (hamstring), running back Trey Sermon (hamstring), defensive end Titus Leo and linebacker Liam Armstrong did not practice. Downs was wearing a boot on his right ankle and using a rolling knee scooter.

Veteran defensive tackle Raekwon Davis remains on the non-football/illness list due to high blood pressure. The Colts are hoping Davis does not have to miss regular-season time.

“I hope not,” Steichen said. “He’s progressing well, so hopefully he’ll be out there sooner rather than later.”

Quick hitters

Carlies was back in pads, but he spent chunks of the team portions running off to the side to get his conditioning back up after not being able to use his lower body for a couple weeks. ... Adetomiwa Adeboware continues to flash his power and disruption against the run, as he swallowed one 11-on-11 play on his lonesome and earned some loud praise from his coaches. ... Cross played a good amount of free safety with the second team in addition to some free and strong with the first team, likely to get more reps and more tests in what's becoming such a critical third season for him. ... Buckner and Grover Stewart swallowed the zone-read rushing attack when they were in the game, but the Cardinals were able to rip off some chunk runs whenever one of them went out. The Colts badly need a backup nose tackle to step up until Davis is able to get over his blood pressure issue and get onto the field.

Contact Nate Atkins at natkins@indystar.com. Follow him on Twitter @NateAtkins_.

This article originally appeared on Indianapolis Star: Colts camp observations: Secondary concerns mount against Cardinals