The 2015 NFL season once again featured heavy playoff fluctuation, with four new teams making the playoffs and four teams falling short of a return trip. It's funny to think about these teams now: how on earth were the Colts not winning the AFC South last year? Turns out a lack of defense and a several major injuries to a star quarterback are a recipe for bad football.

The NFL almost always features several teams who will make a leap up in the standings, either as a result of smart offseason additions or simply because they were dealt a better hand. Then there are the teams who drop off, either because they made mistakes or the ball bounced the other way, both in a literal and metaphorical sense.

Let's identify some candidates to rise up in 2016. We'll hit four that fall back later.

Dallas Cowboys

2015 Record: 4-12

2016 Over/Under: 9.5

Overview: The Cowboys of 2014 set the bar high, winning 12 games and establishing a devastating rushing attack built on DeMarco Murray running behind the best line in football. Dallas let Murray walk in free agency and watched both Tony Romo and Dez Bryant spend the 2015 season being injured, while Greg Hardy drew the public eye on a bad Cowboys football team. The Cowboys were still borderline close to winning the division anyway: an ugly win on "Monday Night Football" in early December had them in the playoff hunt. They wouldn't win another game.

Why they'll make the playoffs: You don't get much less lucky than the Cowboys in 2015. Their best players all got hurt and they went 2-6 in one-score games, including a pair of overtime losses to the Saints and Eagles. Their luck should regress to the norm, although it's worth noting their Expected Win-Loss (explained here, essentially utilizing points for and points allowed to generate an expected record for a team) was 5.2.

Like most teams, their season hinges on the health of their quarterback. An injured Romo will cause major issues. The running game should return to form though. Darren McFadden averaged 4.6 yards per carry behind a Dallas line with multiple Pro Bowl players (Tyron Smith, Zach Martin, Travis Frederick). The addition of Ezekiel Elliott in the draft gives Dallas a legitimate bell-cow back who is also an underrated receiver and a tremendous pass blocker (a trait that should help Romo's health). Dez Bryant is a top-five wideout in the game -- his injury, a Jones fracture in his foot, is concerning, but Julio Jones suffered the same injury in 2013 and returned the following year to post a 1,593-yard season.

If everyone stays healthy and Elliott meets expectations this is top-five NFL offense that can run roughshod through a questionable division. Dallas' offense being better this year than in 2014 isn't out of the question.

If Tony Romo and Dez Bryant can stay healthy, watch out. USATSI

Why they won't make the playoffs: On the other hand, the defense probably won't be better. DeMarcus Lawrence is facing a four-game suspension. So is second-year pass rusher Randy Gregory, who has a history with off-field issues. Rolando McClain will miss 10 games as a result of a suspension. Hardy is gone. Jaylon Smith was a second-round pick and might be a great player but isn't expected to have an impact this season. Morris Claiborne and Brandon Carr remain prominent members of the secondary after failing to live up to their respective hype. Rod Marinelli is a great coach but he's really got his work cut out for him. Romo is pretty old -- the long-time Cowboy turned 36 in April and despite what he thinks, he has a history of suffering injuries. It's absolutely possible Romo gets hurt again, the defense is terrible and Elliott struggles to adjust, while neither Kellen Moore or Dak Prescott is capable of leading this team to an above-.500 record.

Indianapolis Colts

2015 Record: 8-8

2016 Over/Under: 9.5

Overview: The hype for the Colts offense, thanks to additions of Frank Gore, Andre Johnson and Philip Dorsett, was off the charts before 2015. In hindsight, that was pretty dumb! Two big-name veterans and a rookie wide receiver aren't going to overcome issues on the offensive line.

Despite finishing in the bottom half on offense (24th in points, 28th in yards), only getting seven games out of Andrew Luck and being forced to play Matt Hasselbeck (8 games), Charlie Whitehurst (4), Josh Freeman (1) and Ryan Lindley (1) at various points of the season, the Colts still won eight games. Ryan Grigson accidentally put things on the "All-Madden" setting and forgot to turn it off. You just tip your cap to the computer and move on.

There was also a debilitating internal controversy between Jim Irsay, Grigson and coach Chuck Pagano. Everyone was pretty sure not making the Super Bowl would result in Pagano getting the boot, but he found his way back in the offseason.

Why they'll make the playoffs: The smartest move of the offseason was drafting Alabama center Ryan Kelly in the first round. He immediately becomes the Jeff Saturday to Luck's Peyton Manning, a cerebral player in the middle of the offensive line who will have a trickle-down effect on players around him when it comes to keeping his quarterback protected. Luck signed a massive contract this offseason and the Colts are dead set on protecting their investment.

Lots of people are kind of down on Luck suddenly, which is odd considering just how good a player he has been during his time in the NFL. He got hurt and had a rough season, but he's basically been a surgeon forced to operate with a butter knife and a slightly dull stick during his NFL tenure. Expect some weapons to take steps forward this year. The running game should improve with Kelly on the line. Donte Moncrief is on everyone's "breakout receiver" list and for good reason -- he finished with 733 yards despite that list of quarterbacks. He also had 351 yards with Luck under center despite two of those games coming against the vaunted defenses of Denver and Carolina. Dorsett should take a step forward in Year 2 as well and provides another terrifying deep threat alongside T.Y. Hilton.

The Colts outperformed their Expected Win total once again in 2015, as they should have won just 6.1 games. That's cause for concern but you can chalk some of it up to the issues at quarterback. The AFC South remains a very winnable division.

A healthy Andrew Luck in 2016 should do wonders for the Colts. USATSI

Why they won't make the playoffs: But the AFC South is also better than it was in 2015. The Jaguars are a franchise on the rise, but it also feels like a LOT of people expect big things in Jacksonville and it could be a year too early for them. The Texans upgraded at quarterback, running back, wide receiver and could get a full healthy year of the Jadeveon Clowney and J.J. Watt combo. The Titans brought back Mike Mularkey! It's also not difficult to see a similar year for Indy: is everyone really on the same page in the front office? Can the offensive line actually protect Luck? Will the young weapons take a step forward? Is the defense actually any better? You can't guarantee "yes" as an answer for any of those questions.

San Diego Chargers

2015 Record: 4-12

2016 Over/Under: 7.0

Overview: Not the AFC West team you were probably expecting here, but no one is talking about the Chargers. Seriously, find someone (else ...?) who is going to predict an AFC West title for San Diego before this season. The Chargers were a mess in 2015 -- any team with a true franchise quarterback that only wins four games either made some really dumb moves or suffered some horrible luck.

It was mostly the latter for San Diego, which went 3-8 in one-score games and had an Expected Win total of 6 games. In a Week 8 game against the Ravens, an astonishing 12 players left the game with injury (not including six who were out prior to the game). Philip Rivers is not one to make excuses but even he said "I've never seen anything like it" after the three-point loss. Keenan Allen was knocked out with a lacerated kidney, robbing Rivers of his top playmaker. Melvin Gordon was not, ahem, the player anyone expected him to be out of the backfield.

Why they'll make they playoffs: Better luck is the biggest reason for expecting an improvement in 2016. If the Chargers deal with the same rash of injuries they suffered in 2015 (and they've dealt with these issues before) then we can start potentially pointing fingers somewhere other than "football is just hard, man." The one-score game record isn't a guarantee to improve, but history tells us it should.

The running game is still a real concern after offseason micro-fracture surgery for Gordon, but with Ken Whisenhunt back in the fold as offensive coordinator, Allen returning, the addition of Hunter Henry and Travis Benjamin (one of the most underrated signings this offseason for his fit there), Rivers should be in line for another big year. Expectations are surprisingly suppressed for No. 3 overall pick Joey Bosa, who has already made an impression on his veteran teammates. People worry about his fit as a 3-4 end, but he's excellent against the run and Rivers is already raving about the first-round pick. There's a ton of talent on this defense, it just hasn't all clicked yet.

The addition of Joey Bosa should help the Chargers rebound in 2016. USATSI

Why they won't make the playoffs: Maybe the defense won't click. Maybe the Chargers run game isn't established because Gordon's surgery robs him of explosiveness and Brandon Olivier/Danny Woodhead aren't enough to make up for it. San Diego, like New England, isn't afraid to eschew the run for the short passing attack but you need something. Maybe the division is tougher than people expect and the Raiders/Broncos/Chiefs are all making runs at the playoffs.

That's the most likely issue. While the Super Bowl champion Broncos lost Peyton Manning, Brock Osweiler, Malik Jackson, Danny Trevathan and are probably starting Mark Sanchez/Trevor Siemien/Paxton Lynch at quarterback, they've still got an outstanding defense. The Raiders are WHITE HOT in terms of people being on the bandwagon and there's some legitimacy there. And the Chiefs remain steady under Andy Reid, who might have pulled off the best coaching job of his career last season.

Oakland Raiders

2015 Record: 7-9

2016 Over/Under: 8.5

Overview: Seriously -- the Raiders are the team du jour for the offseason, with plenty of people preparing to pick them as the AFC West winners based on a strong core of young talent and a slew of smart offseason moves. The trio of Derek Carr, Amari Cooper and Khalil Mack is reasonable reason for excitement, even if it might be wise to throw a little caution to the wind on the quarterback situation. A surprising 7-9 season in 2015 hit their Expected win total on the nose and featured a ton of growth from the team on both sides of the ball. Carr completed 61 percent of his passes and threw for 32 touchdowns, while Mack emerged as a future Defensive Player of the Year candidate in just his second season.

Why they'll make the playoffs: It's not unreasonable to expect another step forward for their "Big Three" and if that happens the Raiders will be a playoff contender. They might be the biggest contenders to challenge the Cowboys for the best offensive line in football and added to it in free agency, picking up Kelechi Osemele, in one of the best pickups of the offseason.

Oakland also improved its defense, adding Bruce Irvin to line up across from Mack. Aldon Smith will also return from suspension at some point. And Reggie McKenzie did an outstanding job addressing secondary concerns by signing Sean Smith and Reggie Nelson before drafting Karl Joseph in the first round. He would later lock down David Amerson, a scrap-heap gem who was released by the Redskins and blossomed for Oakland last year. If they all gel in the defensive backfield, look out. For a roster that was burnt to the ground just a few years ago, they don't have a ton of weaknesses.

Derek Carr and the Raiders face huge expectations for 2016. USATSI

Why they won't make the playoffs: Everyone is on this bandwagon. Like, everyone. Because the Broncos took some personnel losses, because the Chargers were terrible and because the Chiefs are boring, it's easy to get hyped up about a team with tons of young talent putting it all together for a playoff run. But a lot of times when everyone in the NFL thinks something is going to happen it doesn't. Is that a particularly logical way of expecting something bad to happen for Oakland? Not at all. But the NFL is a fickle beast.

Additionally, the division could be tougher than expected. The three other teams in the division might not just fall apart. The Raiders' schedule looks easy but they also open with three of four games on the road before closing the season with three of four away from home (which is an entirely different issue all together, not to mention kind of a distraction). It just feels a little weird to pencil the Raiders in as a dominant AFC team -- going 8-8 or 9-7 and missing the playoffs wouldn't be a bad season but it's not like that's the floor either.

Honorable Mention

Ravens: If Joe Flacco is healthy and some weapons in the passing game can emerge, the Ravens will be dangerous. Assuming a bounce back isn't a given though.

Bills: Rex Ryan might be coaching for his job after a bad defensive performance last year. He'll certainly be coaching with his dad (along with brother Rob). Tyrod Taylor staying healthy is paramount.

Jaguars: Another heavily-hyped team in a questionable division, Jacksonville has red flags on three first-round-worthy defensive additions (Dante Fowler, Jalen Ramsey, Myles Jack). Anything other than a monster year from Blake Bortles, Allen Robinson and Allen Hurns would be a big disappointment.

Buccaneers: Jameis Winston could take a big leap and the weapons are there, but the NFC is a tough spot to be. They might be the second-best team in their division though.