HENDERSON — The Raiders put a top-10 scoring defense on the field last season, added star tackle Christian Wilkins to the lineup and then dominated the Las Vegas offense in the early days of training camp.

Then the Raiders played two preseason games and their defense was, well, not top-10 quality.

Coach Antonio Pierce has bemoaned the problems against the run, and there were issues in the secondary in Saturday’s 27-12 loss to Dallas. The Cowboys, playing reserves, successfully threw the ball against a Raiders defense with six starters still in the game.

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Pressure on Lance Lacking Without Starting D-Line

Part of the issue against the Cowboys was that the Raiders’ starting line — the strength of the defense and one of the best in the NFL — wasn’t in the game, so there was no pressure on backup quarterback Trey Lance.

He looked like the draft’s No. 3 overall pick from three years ago rather than a player fighting for a roster spot as he completed 15 of 23 passes for 151 yards, with one touchdown passing and one rushing.

Reason for alarm? Or could too much be read into an exhibition game that probably will be forgotten the moment the season kicks off Sept. 8 at the Los Angeles Chargers? The Raiders conclude their preseason schedule by hosting the San Francisco 49ers on Friday night.

“It’s just a building block,” cornerback Jack Jones said. “We keep going each week stacking brick by brick and day by day. Eventually, we’re going to build a brick wall where it’s unbreakable for us.”

That includes Jones learning from his mistake that gave the Cowboys a touchdown. He bit on an inside fake near the goal line by Ryan Flournoy, who then broke to the outside for the TD catch.

“It’s football. It happened,” Jones said. “I made the corrections. I had bad eyes. I was looking in the backfield. I never saw the receiver.”

Jones gave the Raiders a boost last season when they signed him after the Patriots released him. He intercepted two passes in seven games in Las Vegas, returning both for touchdowns.

In the first preseason game at Minnesota, Jones jumped a route to intercept Vikings quarterback J.J. McCarthy.

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Secondary Looks to Build on Last Season’s Success

Jones is part of a secondary that also returns cornerback Nate Hobbs and safeties Tre’von Moehrig and Marcus Epps. Cornerback Jakorian Bennett, taken in the fourth round last year out of Maryland, replaces Amik Robertson, who signed with Detroit.

That secondary helped the Raiders finish 11th last season in allowing 212.4 yards passing per game.

But it’s the front, led by Wilkins and edge rusher Maxx Crosby, that could be truly elite. Crosby has a nonstop motor even in practice. He has 27 sacks over the past two seasons.

Wilkins began his career as an elite run stopper, and now he has shown ability to get to the quarterback. Add in end Malcolm Koonce and tackle John Jenkins, and the Raiders could build on a scoring defense that was ninth last season, allowing 19.5 points per game.

The line depth, however, could be a real concern, especially after the first two preseason games in which the Raiders gave up 279 yards on the ground.

“It’s just the ability to get off blocks,” Pierce said. “It’s different when you’re in training camp and going against your own guys. You don’t throw nobody on the ground. There’s not a lot of violent sheds. But we need to get back to being heavy-handed, getting off blocks, second-level defenders.

“Then we just need to condense the space. There were too many open lanes where those running backs were coming down full speed down in the second level and even up to our safeties and obviously created big plays.”

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Minshew Talks About Starting Role

Gardner Minshew, who is known for being a spark off the bench, spoke to reporters Tuesday night for the first time since beating out Aidan O’Connell for the starting quarterback job.

“I think any time you step in there as a quarterback, whatever the situation, it’s your team at that point and you have to treat it like that,” Minshew said. “I think we have a lot of stuff we can work on — really get dialed in now, get the reps, get some good conversations with these guys and just figuring out our identity and what we’re going to look like.”

O’Connell began last season as a backup, but was named the starter at midseason and went 5-4 the rest of the way.

“I’ll just try to prepare like I’m the starter every day,” O’Connell said. “I know it sounds cliche, but that’s what I’m going to try to do. I obviously know what it takes to play. I got some great experience last year. I’ll try to support Gardner and be ready to go.”