METAIRIE, La. -- You know about Drew Brees and Sean Payton. You know about the historic 2017 draft class. You know about Pro Bowlers such as Cameron Jordan, Michael Thomas and Mark Ingram.

But the most underrated reason for the New Orleans Saints' resurgence as a top Super Bowl contender is their offensive line -- a group that scouting analyst K.C. Joyner ranked No. 1 in the NFL in his annual fantasy-impact ratings for ESPN.

The Saints have rather quietly made a series of major investments in their offensive line over the past three years while rebuilding their roster during a stretch of three straight 7-9 seasons:

• Acquiring center Max Unger in the blockbuster Jimmy Graham trade with the Seattle Seahawks in 2015.

• Drafting guard Andrus Peat and tackle Ryan Ramczyk with first-round picks in 2015 and 2017, respectively.

• Adding Pro Bowl guard Larry Warford with a four-year, $34 million deal in free agency last year after re-upping left tackle Terron Armstead with a five-year, $65 million extension in 2016.

It's similar to what the Dallas Cowboys did earlier this decade. It helped the Saints finish second in yards per rush (4.66) and lead the league in yards per pass attempt (8.1) while surging to an 11-5 record last season.

"Your ability to do a lot of things offensively hinges upon the play of the guys in front of you. That's the run game, that's the pass game and the screen game, you name it. If they're playing well, then you're able to open up the offense in a way that makes us very dangerous." Saints QB Drew Brees on the performance of his O-line

"I don't think you can even begin to overstate how important that is," offensive line coach Dan Roushar said of the investments the Saints have made in his unit. "It's a talented room."

And, oh, by the way, it's not a bad way to extend the career of the 39-year-old Brees.

The Saints allowed only 20 sacks last season -- the second-lowest total in the NFL in 2017 and Brees' lowest total since 2009.

"You've heard me say this before, I think it's a position group that permeates your team," Payton said. "I think it's one of the more ... if not the most important position group. There's so much they're responsible for. They can bring an attitude to your team, and that can kind of permeate through the locker room. Obviously they're smart. There's a toughness element to them.

"And I think that, generally, when you look at a good football team, you're seeing a team that's got a good offensive line."

People might not realize just how extreme the Saints' roster makeover has been since 2015, because Brees and Payton and general manager Mickey Loomis have all remained in place as the faces of the team. But Brees is one of only six players who have lasted on the roster continuously since 2014.

The Saints didn't necessarily set out to make the offensive line the centerpiece of that roster overhaul. But it worked out that way because of the value that Payton, Loomis and personnel assistants such as Jeff Ireland and Terry Fontenot place on that unit.

The most deliberate move they made was landing Unger in the 2015 trade with the Seahawks -- targeting the two-time former Pro Bowler for his skill set, toughness and leadership.

Although Unger was widely dismissed as the "other guy" in the stunning Graham trade when it happened, he has arguably been the more impactful player since. Unger quickly emerged as a team captain and leader of the Saints' offensive line, and they later signed him to a three-year, $22.25 million extension in 2016.

Loomis recently called him "a little bit of an unsung hero for our club."

Likewise, the Saints targeted Warford in free agency last season because he was an up-and-coming young lineman with the Detroit Lions whom the Saints saw as an ideal replacement for longtime veteran Jahri Evans. Peat (the 13th overall pick in the 2015 draft) and Ramczyk (32nd in 2017) were simply the highest-graded players on their board, even though neither had a clear path to an immediate starting job.

Little did the Saints know that they would need Ramczyk to play every snap in 2017 because of injuries to starters Armstead and Zach Strief (who retired after the season).

"He kind of fell to us at the end of the first round," Loomis said of Ramczyk. "Some of it's a little bit of luck -- and obviously conscious awareness that you're always trying to improve that area of your team and are always trying to create depth."

Armstead, meanwhile, is one of those core building blocks who has lasted since 2013 because of his talent. He was a steal in the third round of the 2013 draft out of Arkansas-Pine Bluff -- and still holds the record for the fastest 40-yard time by an offensive lineman at the NFL scouting combine (4.71 seconds). He would probably have two or three Pro Bowls under his belt by now if he hadn't been battling a nagging series of hip, knee and shoulder injuries for the past three years.

But so far, Armstead has looked like his old self again this summer -- which has led to some rave reviews from past and present teammates such as Strief and Warford.

"Oh, man, it's unbelievable," Warford said. "Even compared to last year, I think he's vastly improved. And that's saying a lot, because he was damn good last year. ... It's unbelievable to watch. I'm really excited to see him this year. I think he's gonna be a dominant player.

"His ability to sit on a bull-rush right now -- just watching that, I get jealous."

The Saints' balance might be their most impressive trait. New Orleans was one of only two teams to register A-level grades in pass-blocking, run-blocking and stability/consistency, according to Joyner's grading formula. The Saints have long excelled in the screen game, as well.

Last season, Saints rookie running back Alvin Kamara and Ingram became the first duo to each surpass 1,500 yards from scrimmage in the same season. And though Brees threw the ball less per game than he ever had in 12 years with the Saints, he set the NFL record for completion percentage (72.0) for the third time in his career.

Roushar, who deserves plenty of credit after being promoted from tight ends coach in 2016, is hardly letting his unit rest on its laurels, though.

He stressed that the line still has room to grow. And Unger said Roushar "knows what has been put into it -- and he's grinding; he's making sure that we know there's room for improvement.

"This is a very good group," Unger said. "I've been on some good ones in my career, and we have a chance to be as good as any -- if not better."

The Saints have had some good ones before, too -- great ones, in fact. Guards Evans and Carl Nicks were first-team All-Pros during the era when the Saints won a Super Bowl after the 2009 season, then set the NFL record with 7,474 yards gained in 2011. But both Evans and Nicks were mid-round picks who turned into home runs. This unit is made up of more blue-chippers.

Either way, Brees said there's nothing like a great offensive line to make a quarterback's life easier.

"It totally does," Brees said. "Your ability to do a lot of things offensively hinges upon the play of the guys in front of you. That's the run game, that's the pass game and the screen game, you name it. If they're playing well, then you're able to open up the offense in a way that makes us very dangerous.

"We've been very fortunate over the years to have great guys -- not only good players, but great leadership, great character, and great toughness across the board with our offensive line. This group is one of the best we've had in regards to all those things."