SPARTANBURG The Panthers began training camp three weeks ago wondering about the health of linebackers Thomas Davis and Jon Beason.

They broke camp Wednesday still uncertain about the status of the two defensive leaders.

Davis and Beason, coming off season-ending surgeries in 2011, suffered setbacks that kept them out for long stretches of camp. Beason pulled a hamstring – an injury he says resulted from overcompensating for his surgically repaired Achilles.

Davis, who has had three ACL surgeries on his right knee, strained his right calf during the second practice. Davis has resumed individual drills and coach Ron Rivera hopes he can increase his workload next week.

Neither is expected to play Friday against Miami. Beason hopes to be back for the exhibition against the Jets on Aug. 26.

“That was the timetable we set when I first did it. Obviously, if I don’t feel 100 percent, 90 percent’s not going to get me on the field for that (Jets) game,” Beason said.

Beason said he would be back for the regular season opener at Tampa Bay “for sure.”

Rivera conceded he’s “a little bit concerned” about Beason and Davis, who is attempting to become the first player to come back from three ACL surgeries on the same knee. With the emergence of rookie linebacker Luke Kuechly, the Panthers don’t need Davis to be an every-down player.

“I think Luke and James Anderson are both cornerstones for us right now as far as a linebacking crew,” Rivera said. “We do look forward to getting Jon back on the field and having Thomas contribute to what we want to become as a defense.”

Position battles continue

KICKING COMPETITION: No position battle received as much attention as the kicking competition between veteran Olindo Mare and Justin Medlock, a former CFL star. Mare is close to automatic from inside 40 yards, but the 39-year-old has been short from 50 and out.

Mare gets plenty of distance on his kickoffs – he nailed the crossbar with a kickoff Wednesday. But Medlock has been more accurate on long field goals.

Medlock must prove he can handle the pressure of kicking in the NFL. He badly mishit his first kickoff last week against Houston, resulting in a 90-yard touchdown return by Trindon Holliday.

NO. 3 RECEIVER: The Panthers are counting on third-year wideout Brandon LaFell to complement Pro Bowler Steve Smith. But after those two, it gets dicey.

Louis Murphy, acquired in a trade with Oakland, brings a Jeremy Shockey-like edge to the offense, but dropped several passes in camp. Kealoha Pilares and Seyi Ajirotutu have yet to prove they can be consistent threats in the passing game.

Smith likes what he’s seen from Murphy, who wanted out of Oakland after an injury-plagued 2011.

“When we came in, he said, ‘I need this.’ And when you hear that from a guy, and then he comes out and does it, that’s the part where you realize we need more guys like that,” Smith said. “There are a lot of guys who come in and say they’re hungry and you get two weeks in and they get comfortable and you forget about them and you don’t even know they’re playing.”

PASS RUSH: The Panthers were a week into camp when Rivera said they needed more from Charles Johnson, the $76 million defensive end who had nine sacks last season. The return of defensive tackle Ron Edwards from triceps surgery has solidified the interior, but the Panthers still are not generating a consistent pass rush.

The Panthers had three sacks in last week’s exhibition against Houston, but none by a starter. Unless the front four starts collapsing the pocket, the secondary will get exposed.

What the Panthers learned

CAM, PART II: Rivera knows Cam Newton won’t be sneaking up on any teams. The AP Offensive Rookie of the Year is a known commodity after his record-breaking season of more than 4,000 passing yards and 35 total touchdowns.

Now, Newton is starting to grow before Rivera’s eyes.

“He works on everything. He talks about what he wants to improve. The one thing you really watch – and he’s so hard on himself – is the mental aspect of the game,” Rivera said. “When he’s not making the right decisions he’s missing things, he’s going right to (offensive coordinator Rob) Chud(zinski), right to (quarterbacks coach Mike) Shula and they’re trying to get those things worked out.”

Newton’s certainly not immune to mistakes. Last season he had 17 interceptions, and he threw several at camp, as well. He said one of his offseason focuses was to cut down on his giveaways, and he had no turnovers in three series Saturday against the Texans.

“As a coach, you say I wish I had 52 other guys like him, and we do. We have a lot of guys who are taking (training camp) seriously: Steve Smith, Jordan Gross, Ryan Kalil and Jon Beason,” Rivera said. “They take what we’re doing very seriously. As we grow, the one thing we have to do as a football team is mature, and that goes for Cam. He’s maturing.”

Lessons from camp

RETAINING THE PLAYBOOK: With a lockout-shortened training camp last season, offensive players struggled early on to digest the playbook brought in by Chudzinski.

But with a full camp, as well as new CBA rules on practices, Carolina’s offensive weapons have become more comfortable with the plays.

“Last year with the lockout, we literally came in here and we were just doing it. We didn’t have time to sit down and find out why exactly this was called that and what that meant,” Smith said. “This time we had the opportunity to have a lot of ‘aha’ moments, where you say, ‘Oh, that’s why that’s called that,’ and understand the whole concept of the play.”

YOUNG, DEFENSIVE PLAYMAKERS: Kuechly, the No. 9 overall pick, commanded plenty of attention. For a stretch, the linebacker known for his tackling in college seemed to get an interception every day in Spartanburg.

Now, rookie cornerback Josh Norman has taken over as the primary young ball-hawk for the defense. On Tuesday, Norman picked off Newton and the other quarterbacks four times.

“He’s definitely been a ball-hawk. I’ve watched Luke make some plays, too. … They’re going to try the rookie. And he’s made them pay,” veteran linebacker Jon Beason said. “And that’s what you’re supposed to do if you’re a game-changer or if you’re saying, ’I was a late draft pick, but I can play in this league.’ ”