ALLEN PARK, Mich. -- Jim Caldwell rarely expresses disappointment in individual players, but this was different for the Detroit Lions head coach. This was something that could have been easily avoided.

Considering his team's issues along the defensive line, it’s understandable the fourth-year head coach would be at least a little bit perturbed. Defensive end Armonty Bryant is suspended for the first four games of the season. Tackle Khyri Thornton will miss the first six games. Both violated the league's substance-abuse policy. Both were brought back to the Lions this year -- two of the few free agents who were retained -- to give depth and stability to a defensive line needing improvement.

“The league has rules,” Caldwell said. “We have rules in place and those two guys broke the rules. You break the rules and there’s penalties. They’re going to serve their penalties. We’re disappointed in them, upset with them, the whole bit, but the fact of the matter is, every situation and case is handled differently, so they’ll be punished for it.”

So, too, could the Lions. Thornton and Bryant can practice throughout training camp. They can play in preseason games. But they are hampering a team that is still trying to figure out how to improve a pass rush ranked No. 30 in the league last season and a run defense that allowed 4.37 yards per carry.

And their absence is just the start of the Lions' issues along the line. Bryant is also starting training camp on the physically unable to perform list, one of four defensive ends on the PUP or non-football injury lists along with both potential starters -- Ezekiel Ansah and Cornelius Washington -- and undrafted free agent Jeremiah Valoaga.

Lions defensive tackle Khyri Thornton will miss the first six games of the season because of suspension.. Scott W. Grau/Icon Sportswire

Now it’s worth saying that everything could end up being fine. Ansah and Washington, who were placed on injured lists Saturday, could be back shortly and ready to go early in camp. And the Lions could find another potential gem during camp, as they did last year with Kerry Hyder, who enters 2017 as one of five healthy defensive ends.

But the pass rush was an area that had to be addressed in the offseason and the Lions did, in part, by bringing back Bryant on the end and Thornton on the interior. Detroit signed Washington -- but he is more of a run-stopping edge setter -- as the biggest outside-the-club defensive end signing. General manager Bob Quinn seemed to favor depth over a high-end pass-rushing option, and the Lions didn't draft a defensive lineman until the sixth round.

As the Lions enter camp, the defensive line has to be considered one of the biggest questions on the roster, both with the overall personnel and a group that is starting camp somewhat depleted. That there are injury concerns and suspension issues underlie a looming question for Detroit that will be there at least until games start: How will Detroit put pressure on opposing quarterbacks? The healthy Lions ends – and again, Ansah and Washington could return soon – have a combined 9.5 career sacks.

Create or join a league today >>

Cheat Sheet Central >>

Even if Ansah and Washington come back quickly -- and the Lions can be cautious with Ansah because he’s a veteran with an understanding of the scheme -- Caldwell acknowledged those suspensions are going to alter how the team handles things during training camp.

And that could be something to watch. The Lions will still want to get Thornton and Bryant enough reps to both make sure they are ready for the season and also see if they are good enough to hold onto despite the suspensions.

But they will also have to focus on the players who will be available to them when the season actually starts. Considering how the Lions manage their defensive line, with playing rotations resembling hockey shifts, that will be something defensive coordinator Teryl Austin and line coach Kris Kocurek must balance.

“You have to look at those things and make adjustments,” Caldwell said. “Which we certainly have talked about and will do.”

How the Lions figure all of this out – and whether or not they are able to find consistency getting to the quarterbacks – is going to be a key to Detroit’s 2017 season. And right now, that’s off to a very injury-filled start.