With a quarter of the season in the books, our NFL Nation reporters examine whether these seven teams are legitimate playoff threats.
Last season: 7-9, third place, AFC East
This season: 3-1, including signature wins over Denver (26-16) and Atlanta (23-17).
Why they'll stay in contention: Their defense. The Bills lead the NFL in points allowed per game (13.5) and rank fifth in yards allowed per play (4.73), third in opponent red zone conversions (36.4 percent) and fourth in net yards per opponent pass attempt (5.56). Buffalo also has allowed only four touchdowns this season, the fewest in the league by two, including only one via the pass. The Bills rarely will blow teams out with their offense, so the strength of their defense allows them to play a more controlled style. They've turned the ball over only once compared with seven takeaways, a margin that is tied for second best in the NFL.
Why they could fade: Their roster is not built to withstand many injuries. Entering Week 4, the Bills had been one of the NFL's healthiest teams. They have only two players on injured reserve -- both were hurt in training camp and were not expected to make the team -- and had only three starters miss regular-season time. Their run of good health took a hit Sunday in Atlanta with wide receivers Jordan Matthews and Ramon Humber suffering thumb injuries that will require surgery. The Bills do not have experienced depth at receiver or linebacker -- or at most positions -- so the attrition of a 16-game schedule could wear them down faster than teams with more established depth. -- Mike Rodak
Last season: 6-10, last place, NFC South
This season: 3-1, including a signature 33-30 road win Sunday over the defending Super Bowl champion New England Patriots.
Why they will stay in contention: The nucleus from the 2015 team that reached the Super Bowl remains intact, and overall depth might be better. The defense is the best in the NFL. Cam Newton showed in his statement game against New England that his surgically repaired shoulder is fine, and he's finally grasping how to take advantage of new playmakers such as Christian McCaffrey.
Why they could fade: Start with injuries. Last year's team lost six games by a field goal or less, and catastrophic injuries to the offensive line played a huge role. On Sunday, the Panthers lost free safety Kurt Coleman (sprained MCL) for a month. This team also will struggle if Newton reverts to the way he played in the first three games. The motto here is as Newton goes, so goes this team. -- David Newton
Los Angeles Rams
Last season: 4-12, third place, NFC West
This season: 3-1, including a signature win in Dallas (35-30).
Why they'll stay in contention: The offense should be a legitimate threat for the long term. Their offensive line is better (Andrew Whitworth has been outstanding at left tackle); their receiving corps (Sammy Watkins and Robert Woods) is deeper; and, most importantly, their scheme under first-year head coach Sean McVay is light-years ahead of what Jeff Fisher's staff previously implemented. Also, the Rams' defense is too talented (Aaron Donald) not to improve under Wade Phillips.
Why they could fade: Jared Goff might not be able to sustain this elite level of play. No doubt, the Rams' 22-year-old quarterback has significantly improved since his rookie season. But can he continue to perform like a top-10 quarterback in the NFL? The Rams might need him to for defenses to back off Todd Gurley. -- Alden Gonzalez
Last season: 7-9, fourth place, NFC East
This season: 3-1, including road wins over Washington (30-17) and the Los Angeles Chargers (26-24).
Why they'll stay in contention: As long as the defensive line continues to pressure the quarterback and the offensive front keeps opening up holes, the Eagles are going to be in just about every game. Quarterback Carson Wentz is continuing to develop and is taking more control of the offense pre-snap. Now supported by a strong ground game with LeGarrette Blount and Wendell Smallwood, Wentz has the ability to lead a playoff charge in his second year.
Why they could fade: The corner position has long been a concern. Although the defensive line has helped mask some vulnerabilities, the back end has been susceptible to big plays of late. Ronald Darby dislocated his ankle in Week 1. If he comes back healthy (it's considered a four- to six-week injury), there's a chance the position will stabilize. If he doesn't, Jim Schwartz's defense could wear down as the season goes along. -- Tim McManus
Tampa Bay Buccaneers
Last season: 9-7, second place, NFC South
This season: 2-1, including a 25-23 comeback win over the New York Giants in Week 4.
Why they'll stay in contention: Winning five straight so late in the season last year means you can't ever count them out. They also have a quarterback in Jameis Winston who has shown he can bounce back very quickly from poor performances. He went from throwing three interceptions against the Minnesota Vikings in Week 3 to having a three-touchdown, no-interception performance against the Giants.
Why they could fade: The Bucs' two wins this season have come against two teams that are a combined 1-7. Unlike last year, when they had the league's best third-down defense, the Bucs are surrendering a league-worst 50 percent of their third downs. If that continues, Tampa Bay will have a very difficult time keeping pace with the Atlanta Falcons and Carolina Panthers in the NFC South. Also, it will be very challenging to keep the roster healthy without the benefit of a bye week, which they lost because of Hurricane Irma. -- Jenna Laine
Last season: 9-7, second place, AFC South
This season: 2-2, including a signature win over Seattle (33-27) and a bad loss against Houston (57-14).
Why they'll stay in contention: The Titans play in the AFC South, and none of the four teams has taken control of the division. Tennessee has a good collection of talent, and its physicality on the offensive line and a powerful running back duo in DeMarco Murray and Derrick Henry (Tennessee is fifth overall in rushing at 139 yards per game) make the Titans a prime candidate to get stronger in November and December.
Why they could fade: Tennessee underwent a major overhaul of its secondary this offseason, but it doesn't appear the back end is any better (Tennessee is 29th against the pass, giving up 274 yards per game). Teams are attacking the Titans' cornerbacks with great success, and the pass rush isn't helping their young secondary out consistently. Marcus Mariota's hamstring injury is a reminder that he has to be healthy for them to remain in playoff contention. -- Cameron Wolfe
Last season: 3-13, last place, AFC South
This season: 2-2, including victories over Houston (29-7) and Baltimore (44-7).
Why they'll stay in contention: Though it had a rough day against the Jets, the Jaguars' defense has been the team's strength this season. Cornerbacks Jalen Ramsey and A.J. Bouye are one of the NFL's best tandems, and they're a big reason the Jaguars have 18 sacks. Even though the Jaguars are last in the NFL in run defense (165.5 yards per game), they are second in turnovers (10). The Jaguars had only 13 last season.
Why they'll fade: QB Blake Bortles. He's so erratic, and it's hard to know what he'll be like each week, which makes it hard for the offense to consistently move the ball. When he plays well, as he did against the Ravens and Texans (five TDs, zero INTs), the Jaguars can open up the playbook. When he doesn't, teams are able to stack the line of scrimmage and concentrate on stopping Leonard Fournette and Chris Ivory. -- Michael DiRocco