COSTA MESA, Calif. -- The Los Angeles Chargers open 2022 NFL training camp on Wednesday at Jack Hammett Sports Complex. Here's a closer look at a few storylines.

The player with the most to prove is ... quarterback Justin Herbert: That's somewhat difficult to declare given Herbert's talent and production through two seasons has placed him among the NFL's elite. As a second-year pro in 2021, Herbert's 65.6 total QBR ranked third in the league behind only Aaron Rodgers (69.1) and Tom Brady (68.1). He passed for an eye-popping 5,014 yards (ranked second behind Brady) and 38 touchdown passes (third behind Brady's 43 and Super Bowl-winning quarterback Matthew Stafford's 41).

But this season, with a stacked roster on both sides of the football, the No. 6 overall pick in 2020 must prove that his superior statistics can translate to wins and the franchise's first playoff appearance since the 2018 season.

Most impactful offseason addition ... is impossible to sum up with one name, so let's pick two: Outside linebacker Khalil Mack and cornerback J.C. Jackson. The Chargers commanded headlines in March when they acquired Mack from the Chicago Bears, then signed free-agent cornerback Jackson to a five-year, $82.5 million deal with $40 million guaranteed a few days later.

A three-time All-Pro with 76.5 sacks in eight seasons who was acquired in exchange for a second-round pick and a 2023 sixth-round pick, Mack will line up opposite of Pro Bowl edge rusher Joey Bosa, who has 58 sacks in six seasons, to create one of most-feared pass-rushing duos in the league. And Jackson provides serious ball-hawking skills, as his 25 interceptions since the New England Patriots signed him as an undrafted free agent in 2018 are the most in the NFL. With Jackson's presence, the Bolts will be expected to improve from their 21 takeaways (ranked 17th) in 2021 and get the ball back in Herbert's hands more often.

Training camp will be a success if... the Chargers sign All-Pro safety Derwin James Jr. to a contract extension: The Chargers have several of the NFL's top defensive playmakers firmly under contract, including Bosa, Mack and Jackson. Next up, James.

The 17th overall pick in 2018, James is entering the fifth and final season of his rookie deal and is scheduled to earn $9 million in 2022. A key presence in coach Brandon Staley's defense given his versatility, playmaking skills and leadership, the Chargers must secure the future of the All-Pro safety before the season gets underway.

Despite playing only five games in 2019 because of a foot injury and sitting out the entirety of the 2020 season because of a knee injury, James has established himself among the league's best safeties with five career interceptions, 19 pass deflections, three forced fumbles and 5.5 sacks. His continued effort will be crucial to the improvement of a Chargers defense that gave up 27.0 points per game in 2021, which ranked 29th in the league.

Fiercest fantasy-relevant battle ... Who will back up Austin Ekeler? Ekeler is the Bolts' go-to running back after scoring 20 touchdowns and gaining 1,558 all-purpose yards in 2021. But who will be next in line for carries behind him?

The Chargers utilized a fourth-round pick to select Texas A&M’s Isaiah Spiller, who Staley described as a complete back with an ability not only as a runner but as a pass-catcher. Spiller's addition sets up a competition with third-year pro Joshua Kelley, a former fourth-round pick who has yet to establish himself as a solid No. 2 option after rushing for 102 yards on 33 carries last season. Second-year pro Larry Rountree III, who rushed for 87 yards and a touchdown on 36 carries in 2021, also will compete for touches.

Camp prediction: Spiller will prove himself as potential weapon on offense, earning more than just backup carries behind Ekeler. Rookie running backs can often be slow to ingratiate themselves in an offense at the pro level because of pass protection. However, that might not be the case for Spiller. "He's an excellent pass protector," Staley said, referencing his time at Texas A&M. "Mentally, he was responsible for a lot there. He was a three-down back." Pass protection, along with Spiller's instincts as a runner and hands as a pass-catcher, will enable him to earn playing time early.