Panthers' X factors? Thomas Davis, Cam Newton and more

Linebacker Thomas Davis will miss the Panthers' first four games of the 2018 season as he serves a suspension for performance-enhancing drugs. Chuck Burton/AP Photo

CHARLOTTE, N.C. -- The Carolina Panthers underwent an unusual amount of change during the offseason for a team coming off an 11-5 record and a fourth trip to the playoffs in five seasons.

They begin training camp at Wofford College on Wednesday with new offensive, defensive and special-teams coordinators. They begin with an overhauled receiving corps and secondary. They begin with questions about their franchise quarterback, Cam Newton, who was the league's most valuable player in 2015.

They begin with the heart and soul of the team, outside linebacker Thomas Davis, suspended for the first four games for violating the league's policy on performance enhancing drugs (PEDs).

They begin with a new owner in David Tepper, who replaced team founder Jerry Richardson, who sold the team under the cloud of an NFL investigation into workplace sexual and racial misconduct that resulted in a $2.75 million fine.

They also begin with optimism that they can return to the Super Bowl after losing the title game to the Denver Broncos following the 2015 season.

Here's a closer look at the X factors for the Panthers as they report to camp in Spartanburg, South Carolina:

Cam Newton and Norv Turner: No storyline is bigger than how Carolina's new offensive coordinator will help its star quarterback improve his consistency and overall game. Newton has made progress under Turner, who is installing a scheme with more high-percentage passes to help Newton boost his career completion percentage of 58.3. Turner believes Newton can get his completion percentage into the 65 to 70 range, but there are a lot of obstacles to overcome. Newton also has to adjust to an almost completely new receiving corps, outside of Devin Funchess, so there's a learning curve that will take patience. That Newton hasn't had to deal with an injury -- as he did last year during camp, when he was coming off shoulder surgery -- has helped. That he potentially has more weapons -- and definitely more speed -- around him than he has had at any point in his career also has to help. Adding those ingredients was the focus of the offseason, and general manager Marty Hurney believes that was accomplished, but it's up to Newton and Turner to turn potential into reality after consecutive down seasons by Newton.

Backup quarterback: This will be more of a focal point than ever, with Derek Anderson not in camp for the first time since Newton arrived in 2011. The Panthers made the decision not to re-sign Anderson and instead go with young quarterbacks Garrett Gilbert and Taylor Heinicke. Undrafted free agent Kyle Allen out of Texas A&M and Houston also could figure into this battle. Gilbert hasn't taken a snap in an NFL regular-season game, and Heinicke has appeared in only one game (against the Texans last season), with one pass attempt. There was a confidence level with Anderson that he could win, but the same isn't present yet with Gilbert or Heinicke. Look for Hurney to keep an eye on the transaction list for quarterbacks should things not go well.

Injury list: Backup tight end Chris Manhertz will start camp on the physically unable to perform list (PUP) after suffering a Jones fracture in his left foot during offseason workouts. The injury is similar to what Pro Bowl tight end Greg Olsen suffered last season. Manhertz is listed as the No. 2 tight end, and the staff is optimistic he will be ready for the regular season. ... Middle linebacker Luke Kuechly and defensive end Julius Peppers were limited during the offseason after both had shoulder surgery. The team will be smart in using both early in camp, but they are expected to be ready for the opener. ... Wide receiver Curtis Samuel, whose injury-plagued rookie season ended for good in Week 10 when he suffered a broken bone and ligament damage in his ankle, is expected to be cleared for full participation in camp after getting his speed back faster than expected. Again, the coaches will be cautious with his comeback and perhaps give him a day's rest periodically.

Davis suspension: The three-time Pro Bowl selection will miss the first four games for a failed PEDs test, so that will factor into how the Panthers prepare for the opener against Dallas. Davis will get his fair share of reps early in camp, even though he doesn't really need them at age 35. Shaq Thompson will step immediately into Davis' role when the Panthers go to a two-linebacker set. His role steadily has increased over the past two seasons, and he already was being groomed as the replacement for Davis. The bigger deal will be who steps into Thompson's role when Carolina goes with its base 4-3 scheme. There will be lively competition among David Mayo, Jermaine Carter, Jared Norris and Andre Smith.

Final hurrah? Not much of an X factor, but Davis and Pro Bowl center Ryan Kalil have each said this will be their final season -- although Davis said during minicamp he would now like to play past this season. There has been no communication with Davis on a possible extension and there likely won't be until the season ends. Kalil seems set on this being his final year. Keeping Kalil healthy will be key; he missed 10 games last season with a neck injury. Kalil's neck appears fully healed, and his performance down the stretch last season was encouraging. He's focused on going out on top.

Competition at left guard: The offensive line returns intact, with the exception of left guard, where All-Pro Andrew Norwell signed with Jacksonville during free agency. The competition here will be the most intriguing and most watched of any in camp, with Taylor Moton, Amini Silatolu and Tyler Larsen as the prime candidates. Free-agent signee Jeremiah Sirles also will figure into the mix. The Panthers are high on Moton, a 2017 second-round pick who was a backup right tackle last season. Silatolu has started 31 games for the Panthers, and Larsen proved a worthy replacement for Kalil at center last season. But with Turner determined to focus the offense around the running game and quick passes, replacing Norwell will be key.

Christian McCaffrey's role: He'll play a major part in the offense after the release of Jonathan Stewart. The addition of C.J. Anderson, who rushed for 1,007 yards last season in Denver, will give Turner a nice change-of-pace option. But coach Ron Rivera told ESPN.com he wouldn't be surprised if McCaffrey reached 200 carries in his second year after having only 117 a year ago. The staff is confident McCaffrey can run between the tackles, as he did at Stanford. McCaffrey has bulked up about five pounds to 210 to be better prepared for the pounding. Exactly what his mix of runs versus receptions will be after leading the team with 80 catches a year ago is something to keep an eye on.

Secondary concerns: Outside of the left guard spot, who will play opposite James Bradberry at corner after Daryl Worley was traded to Philadelphia will be the most watched battle in camp. Second-round pick Donte Jackson brings the attitude the Panthers want and haven't had since Josh Norman left following the 2015 season, but the former LSU star lacks experience. Kevon Seymour, Corn Elder Captain Munnerlyn and Cole Luke will figure into the mix. Then there's the safety spot opposite 37-year-old Mike Adams. The Panthers signed veteran Da'Norris Searcy to fill the shoes of free safety Kurt Coleman, who was released for salary-cap reasons. But Searcy is coming off a season at Tennessee where he was replaced as the starter, so he has to prove himself again. There's not much experience behind either starting safety, although the Panthers are high on third-round pick Rashaan Gaulden, who quietly had a solid offseason. The Panthers are one injury away from this being a critical position.

Depth needs: There will an opportunity for fourth-round pick Ian Thomas at tight end with Manhertz out for at least the first three weeks of camp. That position already was hurting for experience after Ed Dickson signed with Seattle in free agency, so Hurney will keep an eye on the waiver wire for depth here in case Manhertz isn't ready for the opener. Veteran talent at safety also will be on Hurney's radar.

Contract extensions: Funchess and right tackle Daryl Williams are in the last years of their contracts, and the Panthers would like to extend both, but there are no active negotiations with either player. Williams is the most likely to get an extension before the season. It might be a wait-and-see game with Funchess.

Ownership transition: Tepper already has given a vote of confidence to Rivera and his staff, so most of his focus has been on the front office. The top priority is finding a new president, a position that hasn't been replaced since Danny Morrison mysteriously left last offseason.