SPARTANBURG, N.C. -- The Carolina Panthers opened 2021 NFL training camp Tuesday at Wofford College. Here's a closer look at a few storylines:

Can quarterback Sam Darnold's career rebound or will he remain at the level he was with the New York Jets?

That’s the $64 million question. Or $23,632,685 since that’s what it will count against the Panthers’ salary cap the next two seasons after picking up Darnold’s fifth-year option. History shows high draft picks that fail at their initial stop seldom recover to be successes. Darnold, 13-25 with the Jets, has a chance at Carolina because he’ll be surrounded by strong offensive weapons in running back Christian McCaffrey, and wide receivers DJ Moore and Robby Anderson, and a good coaching staff. He never had those with the Jets. Much depends on the rebuilt offensive line and Darnold putting behind the “ghosts’’ that made him one of the most inaccurate passers in the NFL the past three years. At least in offensive coordinator Joe Brady there’s a history of turning Joe Burrow from an average quarterback at LSU into the Heisman Trophy winner in 2019.

The Panthers have had 14 different players start at left tackle since Jordan Gross retired after the 2014 season. Have they addressed that with offseason moves?

There is as much mystery here as whether Darnold can turn things around. Carolina signed free agent Cam Erving, who graded out poorly at left tackle for Dallas last season and was a spectator for much of offseason workouts with an unspecified injury. Trent Scott also is an option, but he also missed much of OTAs. Greg Little, who has been plagued by injuries his first two years, also is a possibility. Don't rule out Dennis Daley. Coach Matt Rhule considers Daley more of a right tackle or even a guard but said he looked good on the left side during OTAs. Bottom line, there are no guarantees, which means Darnold could face the same sort of pressure that got him into trouble at New York.

Have the Panthers upgraded the defense with enough pieces to keep them from having to outscore everyone?

Yes. This could be a nightmare for quarterbacks in terms of speed and ability to morph from a 4-3 base to a 3-4 or 3-5-3 without substitution. Carolina added edge rusher Haason Reddick, who had a breakout 12.5 sacks for Arizona in 2020, to play opposite Brian Burns, who had nine sacks a year ago. DaQuan Jones was added to play inside with 2020 first-round pick Derrick Brown. Free agent acquisition Morgan Fox can apply pressure from end or tackle. Denzel Perryman is an upgrade from Tahir Whitehead if he can stay healthy at middle linebacker. Then there’s the secondary where 2020 rookie of the year candidate Jeremy Chinn moves from OLB to safety and first-round pick Jaycee Horn looks like the real deal as a shutdown corner. This could be a top 15 unit if it continues to improve the way it did the final six games last year.

What will a healthy McCaffrey do for the offense?

Let’s forget the Panthers haven’t won their last 11 games when the most versatile back in the league was healthy. The key here is the offense is more explosive with McCaffrey, who in 2019 became the third player in NFL history to top 1,000 yards receiving and rushing in the same season. The Panthers averaged 26 points in the three games McCaffrey played last season, 20.9 points in the 13 he didn’t. For a team that lost eight games by eight or fewer points a 5.1 differential likely cost it a few wins. McCaffrey definitely should make Darnold better. He’ll give the third pick of the 2018 draft a security blanket he never had with the Jets and could help improve his career 59.6 completion percentage.