We talk a lot about the 17-week NFL season as a marathon, and that's a justifiable metaphor; a lot can change over the course of four months. But it's also true that the winnowing begins quickly. Just three weeks into the season, more than a quarter of the teams in the league are either unbeaten or winless.
The four winless teams -- Chicago, Cleveland, Jacksonville and New Orleans -- must contend with this sobering fact: Since 1990, only three of 128 teams that began 0-3 made the playoffs (2.3 percent).
For the five teams that stand undefeated -- Baltimore, Denver, Minnesota, New England and Philadelphia -- there's still some uncertainty. Since 1990, 75.6 percent of teams that started 3-0 (99 of 131) went on to make the playoffs. So it's quite possible that there's an impostor or two in this bunch.
Of the five 3-0 teams, three of them have won Super Bowls in the past four years, and three were playoff teams in 2015. Also, two of them were undefeated at this point last year.
Yet two of the teams are coming off losing records, two have started a rookie quarterback and one has a rookie head coach. In short, if you were asked on Labor Day to pick five teams to go 3-0, this would have been an unlikely list.
Additionally, four of the five teams began the season with massive uncertainty at the game's most important position. The Patriots, of course, were forced to begin the season without their future Hall of Fame quarterback, thanks to a four-game suspension. Meanwhile, the Vikings' starting QB suffered a season-ending injury in late August, prompting them to trade for the Eagles' starter, which in turn led Philadelphia to promote its rookie signal caller to the top job. Lastly, the defending world champion Broncos handed the starting job to a player who'd taken one snap -- a kneel-down -- as a professional.
The fact that this diverse group of teams will head into October without a loss is pretty extraordinary. Let's take a closer look at each situation:
Next opponent: vs. Oakland Raiders, 1 p.m. ET on Sunday.
Ever since the Ravens won the Super Bowl at the end of the 2012 season, they have been a team in transition. Before the title-defense campaign began in 2013, Ray Lewis retired and Ed Reed wasn't re-signed. Haloti Ngata was gone by the beginning of 2015. Now, in the Ravens' fourth season since hoisting the Lombardi, they're still rebuilding -- not around the defense, but around Joe Flacco and his $120.6 million contract. But through the first three weeks of 2016, Baltimore once again finds itself dominating the defensive side of the football -- ranking among the top eight teams in all major defensive categories. And the two sacks from old warrior Terrell Suggs last Sunday indicates that he still has something left in the tank.
Yet, on the offensive side of the ball, the Ravens have scored just 19 points per game and rank among the NFL's worst teams in total offense and rushing yards. The closest thing they have to an offensive playmaker is veteran wideout Mike Wallace, who has their only three receiving touchdowns on the season, but has yet to catch more than four passes in a game and has just one explosive play of more than 20 yards. Meanwhile, the Ravens' longest run of the season has gone for just 15 yards, and their best rushing game came against the Jaguars this past week, when they still averaged just 3.8 yards per carry.
This might also be a good time to mention that Baltimore's opponents are a combined 1-8 on the year. The Ravens are definitely better in 2016, though it's premature to declare how much better.
Next opponent: at Tampa Bay Buccaneers, 4:05 p.m. ET on Sunday.
I have eaten a lot of crow over the course of 2016 calendar year, thanks to the Broncos. After sticking a fork in them during last season's playoff run and predicting a potential 0-3 start with Trevor Siemian at the helm, I think I have finally learned my lesson.
This team is for real -- again -- and it's because this year's Broncos are succeeding in an area where they were consistently deficient during the early stages of their Super Bowl season in 2015. The Broncos again have a dominant defense with a scary pass rush and two of the best cover corners in the entire NFL, but it's the offense -- and particularly, the running game -- that sets them apart from others on this list. Last year, the 3-0 Broncos averaged just 57 yards rushing over the first three weeks. This year, they have nearly doubled that production, averaging 111 rushing yards per game -- and that includes last week, when they had just 52 yards on the ground. Instead, in the victory over the Bengals, it was Siemian who stepped up by throwing four touchdown passes and carrying this offense -- something I wasn't confident he could do a few weeks ago. He isn't going to be an All-Pro, but he's showing signs of competence. And with this defense -- as well as those receivers and an established running game -- competent might be enough.
Next opponent: vs. New York Giants, 8:30 p.m. ET on Sunday.
The Vikings took a major step forward last year, and they came into this season as a sexy Super Bowl pick. Then QB Teddy Bridgewater suffered a freakish, season-ending knee injury in practice. In the immediate aftermath, there was talk that Minnesota's season was over before Labor Day. But then they made the trade for Sam Bradford.
The Vikings prevailed in Week 1 without scoring a single offensive touchdown (with Shaun Hill starting, since Bradford had only been in the building for a week). But then Bradford outperformed Aaron Rodgers in Week 2 and the Vikes topped the Packers. Yet the doubters started in again, as Minnesota lost the best running back in the game in Adrian Peterson. (Yes, I know Peterson was averaging just 1.6 yards per carry on 31 attempts, but if you think he wasn't influencing defensive strategy, you are sorely mistaken. Trust me: Bradford would much rather drop back against a defense stacking eight in the box to stop the run.) Despite those two body blows, Minnesota went to Carolina and beat the defending NFC champs, 22-10, shutting them out for the final 50 minutes of the game.
For the time being, the Vikings have answered all the questions, and they have done it against a solid list of opponents. But they need to continue to develop an offense that currently is averaging just 21.3 points (20th in the NFL), 265.3 yards (31st) and 51 rushing yards (32nd) per game.
New England Patriots
Next opponent: vs. Buffalo Bills, 1 p.m. ET on Sunday.
Bill Belichick is so good, he makes people say ridiculous things. With Tom Brady (in the conversation for Best Quarterback Ever) sitting out four games to serve his Deflategate suspension, New England won its first two games behind Jimmy Garoppolo -- a development that led some imbeciles to wonder if there would be a quarterback controversy upon Brady's return. Then the Pats won their third game, after Garoppolo's injury, with rookie Jacoby Brissett at the helm. In fact, they blew out 2-0 Houston. Afterward, there were people on Twitter -- live, functioning, actual people -- who were wondering aloud if Brady was just a "system quarterback." No, folks, Brady is a great quarterback.
That said, Belichick's system is also the best in the NFL, year in and year out. The Patriot way is surely secretive and at times paranoid, but it's also well-drilled and complex -- and built on a solid foundation. It's telling that Belichick didn't bring in a new quarterback after Garoppolo's injury. He knew Brady was due back after Week 4, and he was happy sticking with Julian Edelman -- a QB in college -- as the backup in the event that Brissett went down.
I predicted this preseason that the Patriots would be the first team to clinch their division and, with the rest of the AFC East now sitting at 1-2, that is already looking like a good bet.
Next opponent (following Week 4 bye): at Detroit Lions, 1 p.m. ET on Sunday, Oct. 9.
When the Eagles shipped Bradford to the Vikings a week before the season started and announced Carson Wentz would be their starter, I supported the move. I've felt for some time that in the impatient world of the modern NFL, when you draft a quarterback near the top of the first round, you must start him at some point in his rookie season, to begin his development and to find out what you're working with. But Wentz was a guy who had appeared in part of just one preseason game and was coming off a rib injury that probably hadn't fully healed. Well, five touchdowns, zero turnovers and three wins later, Wentz has first-year head coach Doug Pederson and GM Howie Roseman looking nothing short of brilliant. Wentz has looked poised under pressure, throws the ball with both touch and zip, and controls an offense like a multi-year vet.
But while we have talked up Wentz's performance ad nauseam, it's perhaps the Eagles' defense that is most shocking. This unit ranks No. 1 in points allowed, No. 2 in rushing defense and No. 4 in total defense. They ranked 28th or worse in all three of those categories last season -- including dead last in rushing defense. New DC Jim Schwartz has done a fabulous job with this unit, but Pederson should get plenty of credit, as well. His offense leads the league in time of possession at 36:47, up more than 10 full minutes per game above last year's Chip Kelly attack (the Eagles ranked 32nd in the NFL in time of possession in 2015), and nearly two minutes better than the next-best team this year.
The Eagles still have some things to prove, but in the very mortal NFC East, they have the makings of a legitimate contender.
Follow Brian Billick on Twitter @coachbillick.