Which former NFL contenders can jump from losing records to the playoffs in 2018?

The Patriots aside, the NFL is a petri dish for league parity. Each year, teams make the leap from losing records to contention — and as the 2017 Philadelphia Eagles proved, sometimes even a Super Bowl title.

In the past five seasons, 18 teams have bounced back from a sub-.500 record to qualify for the playoffs. That’s an average of 3.6 per year, buoyed by last year’s five-team performance; the Eagles, Saints, Panthers, Rams, and Jaguars each went from positions near or at the bottom of their divisions to postseason berths. Several more could make the turnaround in 2018.

The key to these leaps? Big improvements in quarterback play (Philadelphia, Los Angeles) or the emergence of a stout defense (New Orleans, Carolina, Jacksonville). Key acquisitions in the draft or through free agency helped boost the fortunes of these teams, either through headlining contracts like Calais Campbell’s $60 million deal with the Jaguars or overlooked ones like Nick Foles’ $11 million pact with the Eagles.

A few teams are due for a more dramatic turnaround, going from the league’s bottom feeders to potentially vying for a playoff spot in 2018 or 2019. However, these six candidates have all been recent contenders and are looking to shake off a disappointing 2017 to get back into the postseason mix.

The Broncos rode a declining Peyton Manning and a dominant defense to a Super Bowl 50 victory. Over the past two seasons, they’ve backslid thanks to below-average quarterback play and a fierce AFC West. While Case Keenum can’t do anything about the second half of that equation, 2017’s comeback quarterback could be the man to push Denver back to the postseason.

Keenum wasn’t much more than a replacement-level QB before the Vikings and offensive coordinator Pat Shurmur adapted the low-yield passing attack that had worked with Sam Bradford for the former Ram. Keenum responded with the best season of his career — more than 3,500 passing yards in 14 starts, a 22:7 TD:INT ratio, and a top-10 passer rating of 98.3. All of those were better figures than Manning put up in 2015, his last season as a pro and the Broncos’ last playoff appearance.

If Keenum can live up to that standard — Denver will pay him $16 million per year to do so — he’ll have support. Courtland Sutton, Royce Freeman, and Troy Fumagalli should all boost the team’s offense, and the defense is primed to return to its lofty standards. Von Miller’s unit showed signs of regression last season, but drafting No. 5 overall pick Bradley Chubb and the emergence of a handful of young defenders (Justin Simmons, Bradley Roby, Adam Gotsis, and rookies Isaac Yiadom and Josey Jewell) could spark a revival in the Rocky Mountains.

Injuries prevented the Texans from a third straight division title in 2017, but they have the personnel to return with a vengeance in 2018. Houston didn’t get a first-round draft pick after their recent 4-12 disappointment, but the selection they shipped away was part of the deal that brought Deshaun Watson to town — and he’ll the linchpin behind the team’s playoff hopes this year.

Watson’s ascent was quick and impressive. In six starts before tearing his ACL, he led the Texans to three of their four wins, accounting for 290-plus total yards in four different games. His ability to create chaos and extend plays transformed the Houston offense, if only briefly. If he can return to 100 percent this summer, he’ll have to make the most of an offense that didn’t add many weapons behind DeAndre Hopkins and Will Fuller. Still, two newcomers — UCF tight end Jordan Akins and Texas Tech WR Keke Coutee — could contribute right away.

Even if that group of skill players struggles, it will be bolstered by one of the league’s toughest front sevens. J.J. Watt has only played in eight games the past two seasons but hadn’t missed a game before then. At 29 years old, there’s reason to believe he’ll still set the tone for the Houston defense up front. Even if he can’t, Jadeveon Clowney has developed into the kind of pocket-collapsing presence the club hoped he could be when it drafted him first overall in 2014.

There’s plenty of talent surrounding that pair, too — Benardrick McKinney, Zach Cunningham, and the newly signed Tyrann Mathieu will have the chance to thrive this fall. While questions remain about Houston’s cornerbacks, Aaron Colvin’s arrival from Jacksonville should help a secondary that may have a lighter workload than most if the Texans’ pass rush can return to form.

The last time Ryan Tannehill was healthy, the Dolphins were a playoff team. He’s slated to return to the lineup in 2018, and last season’s regression has set Miami up with a favorable schedule. Now the Dolphins will see if a series of questionable roster decisions has given Tannehill the supporting cast needed to win.

Standouts from that 2016 team like Jarvis Landry, Ndamukong Suh, Jay Ajayi, and Mike Pouncey are all gone, mostly victims in some way or another of the team’s awful salary cap management. That still leaves the bones of a useful offense, however. Kenyan Drake ran for 4.8 yards per carry after being given the chance to shine in Ajayi’s absence. Kenny Stills and DeVante Parker are still around to absorb Landry’s targets, and they’ll be joined by two supportive additions: free agents Albert Wilson and Danny Amendola. If a top-10 offensive line can keep Tannehill upright and healthy, the Dolphins will score points.

They’ll need to. Last year’s team gave up nearly 25 points per game and has since lost starters Suh and Lawrence Timmons, though neither lived up to their pre-Dolphins reputations. Robert Quinn can replace some of that production, particularly as a pass rusher opposite Cameron Wake. Draftee Minkah Fitzpatrick, a potential steal at No. 11, could create one of the league’s best safety tandems alongside Reshad Jones. If Charles Harris and Raekwon McMillan can make big strides in their sophomore NFL seasons, they could push the club back to the postseason.

Picking the Packers feels like cheating in this exercise — the only reason they saw their eight-year playoff streak end last year was Aaron Rodgers’ shattered collarbone. Not only will he be back at full strength this season, but the franchise also brought on a developmental backup passer with a higher upside than Brett Hundley (3-6 as a starter, zero touchdown passes at Lambeau Field) by swapping cornerback Damarious Randall for Browns starter DeShone Kizer this March.

Trading Randall leaves a hole in an already-depleted secondary, and Green Bay will need a handful of young charges to step up alongside HaHa Clinton-Dix. The club selected two of the 2018 NFL Draft’s top cornerback prospects, Iowa’s Josh Jackson and Louisville’s Jaire Alexander, and each could work his way into a starting role right away. They’ll be counted on to reinforce a defense that ranked 31st in opponent passer rating in 2017 — the Packers made opposing QBs look like the equivalent of Tom Brady last season.

If the team can reliably patch its issues in the secondary and with its pass rush, Rodgers will be primed to raise Green Bay back to the top of the NFC North. A healthy tailback platoon of Jamaal Williams, Ty Montgomery, and Aaron Jones is more than capable of taking the pressure off the passing game. The presence of Davante Adams and Randall Cobb will bring some key continuity to an aerial attack that will be without Jordy Nelson but also added veteran tight ends Jimmy Graham and Marcedes Lewis. The Packers still have holes to address, but a healthy Rodgers alone should be enough to put the club back in playoff contention.

First things first: if current trends hold, Jimmy Garoppolo will pilot the 49ers to a 16-0 regular season. The former Patriots backup is undefeated as an NFL starting quarterback, a mark made even more remarkable by the fact San Francisco was 1-10 before he took the reins last November. With Garoppolo locked into a long-term extension, the 49ers have their franchise quarterback — and the 2018 offseason has been predicated on building around him. Free agents like Weston Richburg and Jonathan Cooper will help his protection up front along with first-round pick Mike McGlinchey. Former Vikings halfback Jerick McKinnon gives him a dual-threat runner/receiver out of the backfield, and second-rounder Dante Pettis will give him another high-yield playmaker alongside Marquise Goodwin.

There are more concerns on the defensive side of the ball. San Francisco had troubles with its pass defense last season, and the hope is Richard Sherman has enough left in the tank to play at a Pro Bowl level in his first year with his former rivals. The team also drafted three defensive backs this year, though only one — Southern Miss’ Tarvarius Moore — was selected before Day 3.

The 49ers will also benefit from a soft schedule, both inside their division and elsewhere. 2017’s last-place finish means games against the Bears, Giants, and Buccaneers could give them some wiggle room for bad weeks. The cloudy futures of the Seattle Seahawks (slowly dismantling the Legion of Boom defense and unable to block for Russell Wilson) and Arizona Cardinals (now dependent on Sam Bradford behind center) will also provide opportunities for important regular season wins.

The Raiders’ outlook depends on the faith put in Jon Gruden, who secured a $100 million contract from a franchise desperate to relive its glory days as a move from Oakland to Las Vegas awaits. The coach-turned Monday Night Football analyst-turned coach has already reshaped his new roster to his liking, jettisoning players like Michael Crabtree, David Amerson, and Marquette King while bringing veterans like Jordy Nelson, Tahir Whitehead, and Doug Martin to the lineup.

In all, Gruden’s team has added more than 20 players in free agency or through trades, to go along with its nine draft picks. That’s a lot of turnover, but key components like Derek Carr, Khalil Mack, Amari Cooper, and an offensive line that featured three Pro Bowlers will all return in 2018.

That lot is the backbone of a 12-win 2016 team, so there’s reason to believe the Raiders can compete again, even after last year’s 6-10 season. Oakland struggled against an upgraded schedule, going 2-8 against teams that finished the year with winning records. This fall the Raiders will have eight games again teams that finished 2017 above .500, and that includes a fading Seahawks squad and the unpredictable Ravens. It’s not difficult to find nine or more potential wins in the Raiders’ schedule — the question is whether Gruden can get his rebuilt team there this season.