The NFL offseason has plenty of storylines as training camps get underway.

But not all storylines are created equal. While some positional battles might be interesting from a team perspective, a battle along the offensive line for a middle-of-the-pack franchise isn't going to change the outlook of the league.

Some undoubtedly will. Certain quarterback battles could swing entire divisions or decide whether teams aim for the playoffs or the first pick in the draft. Other headlines include elite players' returns from injury, potentially market-resetting extensions and high-impact rookies or sophomores who could push contenders over the proverbial hump.

The following storylines are diverse yet singular in their ability to influence how the NFL's 100th season unfolds.

Marcus Davenport's Comeback

On paper, Marcus Davenport played 13 games for the New Orleans Saints last season, recording just 4.5 sacks in the process. 

That wasn't the return the Saints were looking for after sacrificing so much capital, including a 2019 first-round pick, to trade up to get him at No. 14. 

But context matters. Davenport only got on the field in a rotational role as a rookie. Despite this, he looked like the game-changing presence the Saints hoped he would be—until he got hurt in October. He went on to record just 0.5 sacks over his final eight games (including two postseason) before revealing he played through a foot issue that required an operation to fix. 

Davenport wrote the following on Twitter, according to Kevin Patra of NFL.com: "Most people don't know but I had been dealing with what was considered a season ending injury. Lucky I was able to play through the pain and although not a 100 [percent] I [finished] the season. I promise to come back better. Thank you to all that supported."

The Saints need Davenport to step into an every-down role to pair with Cam Jordan this year. If he's 100 percent and playing like he did before the toe injury, the defense could be even better than expected for a team that was potentially one heartbreaking blown call away from a Super Bowl appearance last season.

Josh Rosen's Rebound Attempt

This one is a little more future-leaning than the rest, yet one has to remember the competition to land the draft's top pick is important, too. 

Josh Rosen could end up playing a big role in how the teams at the bottom of the barrel align this season while looking ahead to the next draft. 

Rosen floundered in Arizona under a poor coaching staff for a season before the front office again hit the reset button on the staff and drafted Kyler Murray. Now, he's with the Miami Dolphins and locked in a roster battle with the seemingly ageless Ryan Fitzpatrick. 

The Dolphins are in a massive rebuild, but Fitzpatrick has made a habit of turning in some surprising play and scraping together some wins. Even last year's sub-.500 Dolphins beat teams like Chicago and New England, so if Rosen can't impress enough to earn a prove-it season, Fitzpatrick might help the Dolphins have a bigger-than-expected impact on the playoff race. 

And according to Barry Jackson of the Miami Herald, Rosen has looked like the worse of the two so far. If he can win the gig, the developmental slant of this approach may mean plenty of losses, which could shake up the draft order. 

Of course, this is all dependent upon Rosen's ability to adapt to a new team for the second time in as many years. 

Can Nick Foles String It All Together?

Where will Nick Foles fall on the Nick Foles spectrum for the Jacksonville Jaguars? Will he be the postseason Foles the Jaguars hope he can be? Will he be the regular-season Foles? Will he be more than Blake Bortles could provide? 

The Jaguars planned on a major uptick in quarterback play when throwing $88 million at Foles. And while he's been superb in the postseason for Philadelphia, he's a 30-year-old veteran who has completed just 61.6 percent of his passes with 68 touchdowns and 33 interceptions in 44 career starts. He hasn't attempted more than 200 passes in the regular season since 2015. 

Foles won't have the benefit of watching from the sideline until late in the season anymore. How will he fare with a new supporting cast led by Leonard Fournette behind a line that allowed 50-plus sacks a season ago. 

If Foles comes along well in training camp and meshes with the weapons surrounding him, it stands to reason he'll serve as an upgrade. An already volatile AFC South that featured two playoff teams and three with at least nine wins last season could get even better. 

If he doesn't, Jacksonville could end up like Miami—perhaps in the conversation for a top draft selection. 

Contracts in Dallas

A year ago, the Dallas Cowboys stormed to the top of the NFC East, 10 wins and a playoff berth. 

While it was fun—and so was a playoff win—the looming contract problems presumably had most Cowboys fans anxious about the future. 

Entering training camp, the Cowboys have yet to work out extensions with Dak Prescott, Ezekiel Elliott and Amari Cooper. 

In other words, the Cowboys haven't locked up a franchise passer who at 25 years of age has already thrown for 10,000-plus yards. They've failed to extend an offer to arguably the league's best back and owner of a career 4.7 yards per carry, nor have they secured a No. 1 wideout who cost extra to acquire before putting up 725 yards and six scores in nine games, finally living up to his top-five draft hype. 

Yahoo Sports' Charles Robinson reported Elliott could hold out, too, so this story is just getting started. And in a new NFL world where Le'Veon Bell just sat out an entire season, anything can happen. 

The Cowboys have the look of a contender again, and all three of these players are under contract. But if one or more misses out on camp, it could hinder the unit's regular-season performance, for starters. 

Giants QB Battle

Elsewhere in the NFC East, the New York Giants are going to have to make a call on the Eli Manning-Daniel Jones battle. 

On one hand, the Giants seem like they would like to take a stab at contention again in 2019 with the 38-year-old incumbent Manning, hence signing a free agent like Golden Tate in the wake of other big moves. 

But that requires context: Manning is not just in the twilight of his career; he managed only 21 touchdowns against 11 interceptions last year despite 576 attempts. And despite the best efforts of Saquon Barkley, the team only won five games. 

In a vacuum, trading Odell Beckham Jr. seemed to suggest the Giants were comfortable punching the rebuild button anyway. If they go that route, throwing this year's sixth overall pick to the wolves and letting him learn while Barkley carries the offense makes sense. 

Giants coach Pat Shurmur seems as up in the air about it as the outlook suggests, according to ESPN's Jordan Raanan: "You never know what is going to happen."

Based on what the Giants decide to do, the NFC East could be looking at another worthwhile challenger, or the team will be jockeying for a top spot in the draft—not the playoffs—late in the season. 

Fifth-Year-Option QBs

This is it for the top of the 2015 draft class. 

Jameis Winston, the first pick that year by the Tampa Bay Buccaneers, has had a tumultuous career and gets one more chance under the guidance of new coach Bruce Arians. 

A year ago, Winston only made it into 11 games and threw for 19 touchdowns and 14 interceptions, making his typical mistakes. 

Quarterbacks coach Clyde Christensen likes where Winston is at now, though, according to Zach Seifter of JoeBucsFan: "So, he's improved a ton. He's picked up the system pretty good. We've stressed just learning the system and fundamentals and stuff. And now we'll have to put it together and get better in all the situations and all those things, apply the fundamentals to game situations."

In Tennessee, the Titans had 2015 second overall pick Marcus Mariota on the field for 14 games, but it felt like fewer given his struggles through nagging injuries that resulted in 11 touchdowns and eight interceptions. He's in a contract year, too, and plans on bulking up to help with the durability concerns he's had throughout his career. 

The Titans were one of three teams with at least nine victories in the AFC South last year, so a resurgent Mariota could mean double digits in the win column. Tampa Bay only won five games, but a Winston rebound could equate to a turnaround in an NFC South with three teams that had no more than seven wins. 

These tales start in training camp. If they yield positive results, we may have a couple of intriguing playoff contenders with massive contract extensions to look forward to. If not, two more teams could enter the fray looking for top quarterback prospects. 

Redskins Rookies

The Washington Redskins had more invested in the 2019 draft's opening round than most teams. 

Washington stood pat at No. 15 after being the subject of much speculation about a move up for a quarterback and landed Dwayne Haskins anyway. With Alex Smith sidelined for at least the 2019 season, the Ohio State rookie enters a battle for the starting job against veteran Case Keenum, a castoff from Denver. 

But the Redskins then justified the speculation by trading back up into the first round for linebacker Montez Sweat, who had a reputation as a top-10 prospect before taking an unexpected fall to No. 26. He's tasked with complementing an already-strong defense trying to compensate for the loss of Preston Smith in free agency. 

This is either going to be a success or failure right from the jump in training camp. The Redskins, after all, were playoff contenders last year, starting out 5-2 before falling off the map largely thanks to the injury bug and finishing with just seven wins. 

Haskins faces the usual perils of a rookie signal-caller, though he's backed by a strong running game led by the ageless Adrian Peterson. Sweat has immense physical traits but is perhaps a bit of a project. If Haskins is thriving as a starter, the offense might be able to match a capable defense. If Sweat is pressuring quarterbacks who usually only have to worry about Ryan Kerrigan, the unit will be much improved. 

But those are a lot of "ifs" surrounding two first-year players. That Washington squeaked out seven wins last year was impressive, and it even included a win over Dallas. If the rookies adjust well enough to the pro game, the Redskins should be right back in the playoff chase on a quicker-than-expected turnaround. 

N'Keal Harry's Immediate Impact

The New England Patriots lost Rob Gronkowski to retirement this offseason, yet knowing Bill Belichick, it is only a matter of time before somebody steps in and begins compensating for the lost production. 

That someone could be N'Keal Harry.

Harry, New England's first-round pick this year, is a big-bodied (6'2") wideout from Arizona State known for using his frame to his advantage. He's already made an impression on veterans in camp, according to ESPN's Mike Reiss: 

"There's a long way to go, but when 11-year veteran quarterback Brian Hoyer relays that he has been impressed by 2019 first-round pick N'Keal Harry's improvement on a day-to-day basis, it reflects that Harry has made a favorable first impression on veteran teammates. Hoyer, as much as anyone, knows how challenging it can be for a rookie receiver to assimilate to the Patriots' system, and he said Harry has been fun to work with."

Granted, it is a rarity for rookie wideouts to stand out in Foxborough given the complexities of the Patriots scheme and the demands of playing with Tom Brady. But lining up at different spots and already catching the eye of a respected veteran is a good start. 

Harry isn't going to get a chance to make the in-line blocking difference Gronk made last season, but if he can sniff the 682 yards and three scores, the Patriots might not skip a beat offensively despite losing arguably the greatest tight end of all time.