*Paul Guenther is mixing veterans like Vontaze Burfict with a band of young players that has given the defense a historic start. *

Since the 2009 Bengals shot to No. 4 in defense, they've put together some of the most memorable games and units in franchise history starting with that team's sweep of the AFC North.

But head coach Marvin Lewis has never seen any of his defenses do what the men are doing under defensive coordinator Paul Guenther in the first five of games of this season they are first or second in five categories and are on pace to set 16-game franchise records for fewest yards (4,205) and points allowed (265).

And they've certainly never done it with so many first-year players contributing so many snaps. The motto Lewis put on the 2017 T-Shirts, "Run on your own gas," has received an oil change of youth.

Since linebacker Vontaze Burfict played 886 downs for that sixth-ranked defense in 2012, no rookie defender has played 165 snaps. But two current first-year players, pass rusher Carl Lawson (160) and cornerback William Jackson (154) are going to pass that in the next game. Two other rookies, end Jordan Willis (127) and tackle Ryan Glasgow (108) will get there at the midway point.

And since Burfict, tackle Devon Still (156), and linebacker Emmanuel Lamur (103) played more than 100 snaps during that '12 season, only three rookies have played at least 100 snaps: End Margus Hunt, defensive back Josh Shaw and linebacker Nick Vigil.

Four rookies already have 100 and nose tackle Andrew Billings (41) will make five. Don't count out linebacker Jordan Evans even though he has only 12.

(Jackson and Billing are in their second NFL season, but injuries in training camp wiped out their rookie years so this is the first year they've played in games.)

After racking up six sacks for the second time this season in Sunday's 20-16 win over the Bills when they hadn't had a six-sack game in five years and after already posting two of the top 17 stingiest games in 15 seasons under Lewis, there's only one place to start when looking at the differences between Lewis' great defenses under Guenther and Mike Zimmer.

Youth.

William Jackson (22) is the first-round pick of the first-year players.

 "That's probably true. We have 11 football games for these guys to continue to grow together and play great," Lewis said Monday. "They can play lights-out defense. But they have to do it play after play, and don't let one play bleed into the next play."

  When the 2012 team started 3-5, the defense held foes to less than 13 points per game in the final eight games that featured the 13-10 masterpiece in Pittsburgh that put them in the playoffs. That was the one where Burfict led three rookies with more than 100 plays and only one was drafted, Still.

The 2013 team finished No. 3 in NFL defense while winning the AFC North and that included holding New England without a touchdown for the first time in four years and snapping Tom Brady's streak of 52 straight games with a touchdown pass. That's when Hunt played 164 snaps as the only rookie to play 100.

And the 2015 defense helped them get a dozen wins for the second time in history when they allowed the fewest points in a Bengals' 16-game season they gave up just 37 points in their three division road games. Again, only one rookie played more than 100 snaps and Shaw did it barely with 116.

So it's amazing they've got so many kids playing under Guenther and Lewis because the idea of playing even one rookie seemed to never quite enthrall them.

"My first year in coaching (the) AD told me for every freshman you play, you're going to lose one ballgame," Guenther said with a laugh Monday, the former youngest head coach in America surrounded by the frosh. "It always stuck in my mind. At this point in the NFL the way contracts are constructed you have to get them out there and playing and if they can play you've got to go. I felt good enough in the preseason. We played a lot of these guys early against good guys in the preseason that I spoke about in training camp that I think they kind of get it now."

And it sounds like Lewis has, too. He's never hid his old-school veteran favoritism. But there's one thing more old school than preferring vets and that's winning.

"The human nature — or coach nature — is to throw Michael (DE Johnson) or Carlos (DE Dunlap) back in there," Lewis said. "But then you see Jordan Willis make the plays he's making or Glasgow make the plays. Obviously with the plays Carl is making time and time again, and with Andrew Billings doing a great job inside, and William in the secondary — they're earning opportunity. We have to make sure the level doesn't drop.

Since Carl Lawson's first NFL sack of Aaron Rodgers. he's got 2.5 more.

But not only is there the youth, there's no doubt the best mix of youth and veterans they've ever had under Lewis on defense. The only defense that comes close is that '09 crew where rookie Rey Maualuga was a starting linebacker, rookie Michael Johnson was a regular in the rotation, and rookie Tom Nelson was pressed into service at safety.

And those kids certainly never had a potential first ballot Hall-of-Famer at the three technique on the D-line like these guys have in 29-year-old Geno Atkins. Throw in Burfict and the Bengals just may have the top players in the league at their position.

"The one thing about Geno this year is he has become a mentor. More so than any other year I've been around him," Guenther said. "You all know him as a quiet guy, but I've seen him taking Glasgow, taking Lawson, taking Willis, the inside guys, Billings, and really talking to them about, 'Hey, this kind of protection, this is how they're doing things.'

"Any time you get that kind of feedback as a young player from a guy that has been around here is tremendous. They get tired of hearing me talk for a while. Anytime you can hear from a veteran player you respect, that's big …. He has done a tremendous job this year of being a mentor."

The kids are all right. With 3.5 sacks, Lawson is already threatening Dunlap's club rookie record of 9.5. Jackson survived a major penalty Sunday to come back and make a good play in the end zone while filling in capably for the injured Adam Jones and Dre Kirkpatrick.   Willis hauled down his first NFL sack on Sunday, but he's been getting pressures since he arrived.

It's enough to convince the guys they need to convince. Both Lewis and Guenther were marveling Monday at one lineup they had on the field a couple of times against the Bills. Billings and Jackson. Plus Lawson, Willis, and Glasgow.. Count Vigil and that's half a dozen guys that played 110 snaps combined last season.

 "It's not like I was nervous with them in there," Guenther said. "Those guys can all play. They understand the leverage, the responsibilities. Will they have a hiccup here and there? Yeah, they might."

But not enough, it seems, to sit the kids.

"That's huge that you're getting such positive plays (out of young players)," Lewis said. "We aren't missing a beat."

Heading into the bye, that has turned out to be the motto of the season you can put on one of Lewis' T-Shirts.