DALLAS — The Dallas Cowboys don't have all of their intended top defensive ends in training camp and available for the first preseason game at the San Francisco 49ers. Pro Bowler DeMarcus Lawrence is still recovering from shoulder surgery, Randy Gregory remains suspended and it's uncertain as to whether he has applied for reinstatement, and Robert Quinn broke his hand on Tuesday.

All of this means is it's the perfect opportunity for second-year defensive end Dorance Armstrong to shine.

The 2018 fourth-round pick from Kansas produced a half-sack in 15 games for Dallas, and even started a game. Along with the half-sack, Armstrong collected 13 combined tackles, a tackle for loss, and three quarterback hits. However, unlike regular season action, where there is a clear hierarchy, where mid-roster players and rotational players such as Armstrong have their chance to put on full display what they are capable of is in the preseason.

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According to the Cowboys' unofficial depth chart released Aug. 5, Armstrong was listed as playing behind Quinn. However, now that Quinn is out for the entire preseason with his broken hand, Armstrong is presumably elevated to the top spot, playing as a bookend to a defensive line that features Maliek Collins as the 3-technique defensive tackle, Antwaun Woods as the 1-technique defensive tackle, and former 2017 first-round pick Taco Charlton as the other defensive end.

Through his second training camp, Armstrong has impressed coach Jason Garrett with his determination and spirit.

"He’s come in and been a real determined guy right from the start," Garrett told reporters Tuesday. "You love his spirit. You love his attitude. You love his work ethic. And he’s a sneaky good rusher. He doesn’t overwhelm you with physical traits, like, 'Wow he’s the quickest guy I’ve ever seen. He’s the fastest guy I’ve ever seen.' But technically he’s pretty good.

"He has a good little pass rush repertoire. We saw that in college. We saw that last year. "

At 6-4, 255 pounds, Armstrong has the measurables to contribute to the Cowboys' pass-rush. But to be a "rushman" for defensive coordinator Rod Marinelli, it isn't enough to sack the quarterback; defensive linemen also have to stop the run.

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What is the best thing for the 22-year-old from Houston, Texas? More playing time and more reps — things he gets from having Lawrence, Gregory, and Quinn out of the lineup at the moment.

"Like with all these guys, the more they play, the more they go against NFL players, if they approach I the right way, they’re going to improve and he’s certainly done that," said Garrett. "He’s approached it the right way. Very hard worker. Wants to get better every day. I think you’re starting to see that on the field."

Armstrong will get a chance to show it Saturday night at San Francisco.

Do you think Armstrong will be able to hold down the fort at DE before the cavalry arrives? Share your thoughts on the D-line depth with Mark on Twitter @therealmarklane.