Through the first five weeks of the NFL season, no team has yielded more surprising results than the New York Jets.

The Jets come out of their bye week at 3-1, firmly in AFC playoff position, and just half a game behind the New England Patriots for first place in the East, a quarter of the way through their season. It’s a far cry from what was expected of New York entering the 2015 campaign. But the Jets have achieved early season success in a familiar way, on the strength of a dominant defense implemented by new head coach Todd Bowles and defensive coordinator Kacy Rodgers.

Over their first four games, the Jets have allowed just a shade over 280 yards per game, a total that currently ranks second in the league in yards allowed per contest, behind only the unbeaten Denver Broncos. They’ve also limited opponents to less than two touchdowns per contest, permitting just 13.8 points per game, a shockingly low tally. Look at it this way: through four weeks the Jets have allowed a total of just 55 points. In contrast, the Patriots tallied 51 points in Week 3 alone against Jacksonville.

Despite all that success, Bowles cautioned this week that the Jets can’t get too far ahead of themselves and noted how quickly things can change week to week in the NFL.

“It’s only 3-1, a quarter of the season,’’ the coach said. “We’ve only played one quarter. It’s like a game. The first quarter doesn’t mean you lost the game. The first quarter of the [season] doesn’t mean we got to the playoffs. We’ve got a long way to go. The season’s young. You can go from the penthouse to the outhouse real quick.’’

But there is plenty of reason to believe that New York’s success early this season is sustainable.

The statistics so far for the 2015 Jets fall in line with where New York was in 2009, the team’s first year under former head coach Rex Ryan. That season the Jets allowed just 252 yards and 14.8 points per game, both far and away the best marks in the league. They went on to finish 9-7, second in the AFC East. But their defense pulled them into a Wild Card slot and they parlayed that into a deep playoff run, all the way to the AFC Championship Game, led the whole way by that defense.

New York ranked third in yards allowed per game and sixth in points allowed the following season, finished 11-5 and made another run to the AFC Championship Game. But in the four years that followed under Ryan, they slowly lost their grip as a dominant defense. Ryan’s crew continued to rank among the Top 10 in fewest yards allowed per game over those next four seasons, but they stopped being able to keep teams out of the end zone. Over the final four years of Ryan’s tenure as coach, the Jets ranked, on average, 20th in the NFL in points allowed and their undermanned offense simply could not keep up.

After four years of mediocre at best football, the franchise sent Ryan packing and while many expected them to go with an offensive-minded coach, New York made a wise decision to stick to their strength and re-commit to winning with defense.

They brought in Bowles, the former Arizona Cardinals defensive coordinator, then went on an offseason spending spree to revitalize the defensive unit. That process included bringing back some familiar faces, cornerbacks Darrelle Revis and Antonio Cromartie, and pairing them with some new ones in cornerback Buster Skrine and safety Marcus Gilchrist. The addition of those four revamped a secondary that had become a clear weakness of the defense.

The Jets already boasted one of the league’s best front seven units, and they bolstered it through the draft when Leonard Williams, arguably the most talented player in the class, fell into their lap at No. 6 overall. That pick ended up paying dividends immediately when defensive tackle Sheldon Richardson was suspended for the first four games of the season.

With Richardson out, Williams has been pressed into action and has proven himself as one of the best players on the Jets defense early on. He currently ranks in the Top 10 among 3-4 defensive ends according to Pro Football Focus due to his ability to excel in pass defense and run defense. According to PFF, although Williams has only managed one sack, he has 10 quarterback hurries and seven quarterback hits, the latter being the highest total in the league for a 3-4 DE. He also has nine solo stops, most of which have come against the run.

The only Jets player who has stood out more than Williams through the first quarter of the season has been fellow defensive end Muhammad Wilkerson, who ranks third overall among 3-4 defensive ends according to PFF’s rating system. Wilkerson is in the early running for Defensive Player of the Year due to the impact he’s had for the Jets.

Like Williams, but to an even stronger extent, Wilkerson has been an all-around beast for the New York defense. Against the pass, he has a team-best three sacks, and also has garnered 12 hurries, four QB hits, and has batted down four passes. Additionally, Wilkerson has forced a pair of fumbles and his 13 solo stops are tied for second most in the league.

The impact of Williams, Wilkerson and the rest of the Jets front doesn’t necessarily show up to the naked eye. As a unit, New York has just seven sacks, which has them tied for 27th in the league, although they do have six interceptions, tied for sixth.

New York doesn’t really have anyone whose individual defense jumps off the page. But as a unit it, they’re getting a job done at a very high level, especially against the pass. The Jets boast the league’s second best pass defense through four weeks, allowing just 185.5 passing yards per game, and quarterbacks are completing a league-worst 51.1 percent of their passes against the New York defense.

That’s despite the fact that Revis is the only Jets defensive back rated highly in coverage, according to PFF. Quarterbacks have completed nine of 20 passes thrown at Revis, but much of that comes from Week 2 when he permitted five catches and 75 yards against the Colts on Monday Night Football. Since then, Revis has been at his best, allowing just one two-yard catch between Week 3 & 4. Revis also had an interception in that game against Indianapolis and tacked on another in Week 4 against Miami, raising his success-rate significantly.

In contrast, Cromartie and Skrine both rank in the bottom third in pass coverage rating. Quarterbacks have completed 60 percent of passes thrown at Skrine and a shade over 56 percent against Cromartie, who has also given up three of the five passing touchdowns allowed by New York this season.

Free safety Marcus Gilchrist does boast a slightly above average pass coverage rating, boasted by his play of later. Since the Browns went 3-for-3 on him in Week 1, teams are just 1-of-7 for eight yards when targeting Gilchrist, who also has an interception. But strong safety Calvin Pryor has been somewhat more vulnerable, allowing 52.9 percent of all passes in his direction to be completed.

Taken on the whole, the performance of the Jets secondary all seems very average at best and a realistically closer to a tick below average. But where this group has thrived is in limiting the big play, and therefore keeping opponents off the scoreboard. Through four games, New York has allowed just 12 pass plays of 20 yards or more, tied for fifth in the league and just two plays of 40+ yards, which ranks them seventh.

“Once you go out there and dictate what you want to do, even if a team knows what you’re doing, it shouldn’t matter,” Cromartie told the New York Post this week. “The biggest thing for us is to just go play football. The goal is to be productive and play [lights] out and put it all together.”

Of the five Jets defensive backs seeing the most action, four are allowing less than 13 yards per catch, including less than 10 from both safeties. Only Cromartie has allowed significant gains against him, an average of 21 yards per on the nine catches he’s permitted. But the 10-year veteran has been dealing with a knee injury since Week 1, and it stands to reason he might be better coming off the bye with some time to allow that injury to heal.

The pressure the Jets front has put on quarterbacks has also certainly helped the defense thrive so well, and they’ll get a boost in that regard this week when Richardson returns from his suspension to complement the team’s front trio of Wilkerson, Williams and Damon Harrison. But where Richardson should really help against the run. According to PFF, Richardson was the league’s premier run-stopper among 3-4 defensive ends.

Getting that kind of production back will be a boon for a Jets defense that has been good but not great against the run this season. Currently New York ranks eighth in the league in run defense, allowing 94.8 yards per game on the ground and 3.8 yards per carry. Outside linebacker Quinton Coples is the only one of the four starting Jets linebackers to rate positively against the run according to PFF. Fellow OLB Calvin Pace comes in a tick below average, as does inside linebacker David Harris, despite the fact that Harris is third best overall among 3-4 ILB according to the PFF rating system. Inside linebacker Demario Davis has been the weak link against the run, and putting Richardson on his side when he returns could help shore things up.

“Coach Bowles will tell you, it’s not about what they’re doing, it’s about what we’re doing,” Harrison told reporters this week. “We need to dictate what teams can do. If we can stop the run and force them to pass, that’s great. If we limit the passing and force them to run, then something’s got to give.”

But like the pass defense, though the numbers aren’t all that great overall against the run, the Jets have been stingy when they’ve had to be on run defense as well. In fact, through the first four weeks, New York allowed just one rushing score, a Darren Sproles one-yard run in their Week 3 loss, and they’ve forced four fumbles on rushing plays, tied for third in the league. Additionally, the Jets have allowed just a single rushing play of 20 yards or more, showing that their ability to limit big plays extends beyond the stout pass defense.

Given those statistics, it seems New York is truly utilizing a “bend-but-don’t-break” defense under Bowles and Rodgers, and having quite a bit of success doing so. It’s that mentality that’s been the catalyst for the defense’s overall effectiveness and the team’s prosperity. But the Jets aren’t letting their early success change their mentality. In fact, they don’t look at their first month performance as a success at all.

“No matter how good the numbers look, they’re just numbers,” Harrison surmised. “We’re still nowhere we need to be. Not even close. We’ve done a good job getting by. But we’re not where we need to be.”

The fact that this Jets defense seemingly still has so much room to improve is significant, because the four-week results seem sustainable even without some improvement. And because some of the individual players are playing below expectations, it stands to reason that the defensive unit could get even better as the season wears on.

With Richardson back, the Jets front trio is as deep as they have ever been. In the middle, Coples and Harris have been very good, and Pace and Davis are good enough, with both even likely to tick up a bit. On the backend, Revis has been excellent, but even he is playing below his career norms and has room to improve, as does Cromartie. Skrine has passed the eye-test and should get there as it relates to the stat test as time goes on, and the same is of true of Gilchrist at free safety. Even Calvin Pryor stands to improve as he gets more and more comfortable back at strong safety.

“They still know that we have a ways to go fundamentally and communication-wise,” Bowles said of his defensive personnel. “But they’re getting to know each other and they’re getting better.”

In addition to personnel improvement, the schedule also sets the Jets up for success. The Redskins come to town this week, boasting the league’s 11th best offense, but New York should be able to handle Kirk Cousins and Co. The Jets then make a trip to Foxboro in Week 7, which could be trouble, but they follow that with a visit to Oakland to face the Raiders and then a trip back home to take on the Jaguars, both of which are bottom half offenses.

If the Jets defense can do its job over the next four weeks, and they come away with three more wins to improve to 6-2, they’ll be in prime shape for a playoff run.