Let’s start with a statement few football fans would debate: New England Patriot Tom Brady and New Orleans Saint Drew Brees are really good at playing quarterback. (They’ve combined for five Super Bowl MVPs and 22 Pro Bowls—indeed, Brady can go to parties and do… this.)

You may not appreciate, however, just how historically superb they are, both ranking among the top four QBs all-time in career completions, passing yards, and touchdown passes.

The other two members of the top four are Peyton Manning (retired in 2015) and Brett Favre (retired in 2010).

The top 10 in those categories features three additional active QBs: New York Giant Eli Manning, Pittsburgh Steeler Ben Roethlisberger, and Los Angeles Charger Philip Rivers.

Steadily approaching the top 10 are Green Bay’s Aaron Rodgers (already #9 in touchdown passes) and Arizona’s Carson Palmer…

Wait, Carson Palmer? The Carson Palmer best known for threatening to retire if the Bengals didn’t trade him, which resulted in him being sent to the Raiders, where he went 8-16 as a starter?

Yep, that Carson Palmer. Seems he’s #11 in completions, #13 in passing yards, and #12 in touchdown passes. Even if Palmer never plays another down after his recent injury, he’s still ahead of four-time Super Bowl champ and two-time NFL MVP Joe Montana in all three categories.

No disrespect to Palmer or anyone else on the list, but the NFL was founded in 1920. How is it possible that a majority of the game’s most prolific quarterbacks are either playing now or were in their prime in the last decade? (Hell, three of them came from the same 2004 draft class: Eli and Rivers were traded for each other!)

“By and large, the NFL has really tried to enhance scoring and benefited the offense,” said ESPN NFL analyst Tim Hasselbeck, who’s here to help explain just how the league does this. (Tim is inclined to sympathize with offense: he not only played quarterback in the NFL, but his brother Matt did too.)

Some recent rule changes make it easier for quarterbacks to complete passes. Others just make it possible for them to stay physically intact long after earlier generations had been battered into retirement. Here’s a quick timeline of why today’s defensive coordinators don’t get much sleep.

1993: It is not intentional grounding when a passer, while out of the pocket and facing an imminent loss of yardage, throws a pass that lands beyond the line of scrimmage, even if no offensive player has a realistic chance to catch the ball (including if the ball lands out of bounds over the sideline or end line).

“Take something like the ability to throw the football away. You’re outside the tackle box and all you need to do is get the ball to the line of scrimmage. Obviously that creates a protection for the quarterback.” (Beyond the safety standpoint, this also spares QBs a lot of interceptions, since they can lob the ball where no defender could possibly make a play.)

1995: When tackling a passer during or just after throwing a pass, a defensive player is prohibited from unnecessarily and violently throwing him down and landing on top of him with all or most of the defender’s weight.

“Quarterbacks, when they’re in the pocket… they’ve never been taught to look around at who’s coming to hit them. They’ve been taught to look downfield: you’re looking at the coverage and you’re trying to find who’s open. So when you get hit, you usually don’t know where it’s coming from. I think the league has realized that’s a very defenseless position.”

(As a reminder of how thoroughly linebackers used to be able to manhandle quarterbacks, here’s a short clip of Hall of Fame linebacker Dick Butkus.)

In particular, this rule limiting the force tacklers can use to take down a QB seeks to reduce head injuries: “Oftentimes they drive you into the ground and your head kind of does a double tap on the ground. That’s a reason why quarterbacks for the longest time have been the most concussed position on the field.”

2002: It is illegal to hit a quarterback helmet-to-helmet any time after a change of possession.

This eliminated a particularly ruthless bit of defensive strategy: “It used to be that the quarterback throws an interception, the defenders they were taught, ‘Hey, go find number 14 and hit him as hard as you can. Free shot on the quarterback. Do it as violently as you can.’ That’s changed.”

Hasselbeck also noted that, in the event of a turnover, coaches today will often urge the QB to focus on self-preservation as opposed to try to turn into Lawrence Taylor: “If Tom Brady throws an interception, the idea of taking on a defensive lineman who’s trying to put a block on him on the return, I think most reasonable minds would say that’s probably not a battle we want him fighting.”

2006: Low hits on the quarterback are prohibited when a rushing defender has an opportunity to avoid such contact.

“Preventing guys from being around your feet is a big one for longevity.”

2007: A block below the waist against an eligible receiver while the quarterback is in the pocket is a 15-yard penalty instead of a 5-yard penalty (an illegal cut block).

How many times have you seen a quarterback looking for an open receiver… but they’re all covered… and he keeps looking… and suddenly he’s obliterated for a sack. The NFL strives to reduce these moments. Hasselbeck noted the NFL has put limits on defenders “in terms of how you can make contact with receivers as they’re trying to get open… With the size and athleticism of receivers and your inability to defend them, that’s been a big part of quarterbacks being able to get out of their hand quickly.”

2009: It is an illegal hit on a defenseless receiver if the initial force of the contact by the defender’s helmet, forearm, or shoulder is to the head or neck area of the receiver. Penalty: 15 yards.

“I do believe that as the NFL has looked at making the game safer, one of the things that they’ve tried to do is acknowledge that there are plays where people in general, whether quarterbacks or receivers, are deemed defenseless.”

2009: Clarified rule regarding low hits on passers: A defender cannot initiate a roll or lunge and forcibly hit the passer in the knee area or below, even if he is being contacted by another player.

This is known as the “Brady rule,” because it was implemented after Brady was knocked out for the entire 2008 season by the play below:

Quite simply, rules like this have been a mitzvah for the longevity of QBs across the league: “The effort to keep people off of guys’ knees and the head and neck area is probably the number one thing that has helped guys be healthy each and every week.”

Indeed, Hasselbeck said that rule changes have made it so that defensive legends from earlier decades would have to take an entirely new approach to the game: “[Hall of Fame cornerback and safety] Ronnie Lott was one of the most feared guys because of the way he hit people. He probably wouldn’t be allowed to hit people… not probably, he wouldn’t be allowed to hit people the way he did back when he played. Would he be a guy who was suspended every other week?” (Based on the clips of “The Hitman” in the second half of this video, the answer is, “Oh, most definitely.”)

Even less violent defenders from previous NFL eras would have been impacted: “There are guys who played corner by being physical all the way down the field. They got up and they mauled guys. You’re not allowed to do that any more either.”

If you’re comparing quarterbacks from earlier eras to today’s, it’s worth remembering that far too many older stars had their careers shortened by plays the NFL would severely penalize today: “Steve Young’s career ended because of a brutal hit from Aeneas Williams that knocks him out.” (Note: This play is horrifying.)

Today? “You can’t hit guys like that any more. That extends careers.”

There is also a focus today on quarterbacks keeping themselves on the field: “Sliding feet-first is way more acceptable now than it ever was—in many cases it’s taught.” Indeed, often a quarterback will just “give himself up” for a sack: “That used to be a thing that people would have never thought of doing at the position.”

Taken all together, you have a league where quarterbacks (and their receivers) are safer and there is every incentive to throw the ball: “Quarterbacks have definitely benefited from an interceptions standpoint, a volume of attempts standpoint.”

It becomes reasonable to ask: When we fixate on passing stats, are we selling short the star quarterbacks of yesterday?

Hasselbeck said we may be unfairly dismissive of players from different eras (focusing, for instance, on how Joe Namath threw more career interceptions than touchdowns): “Roger Staubach, I don’t think anybody disputes how incredible he was for the Dallas Cowboys. Then Troy Aikman’s number are better than his and Tony Romo’s numbers are better than his. So you say, ‘Well, Is that a fair indicator?’ Business was being done much differently back then.”

Here’s a crude but effective way to adjust for the fact that modern quarterbacks have both longer careers and typically throw the ball more times each game than their predecessors. Look at the career leaders in yards per pass attempt. There are modern players—those tied for fifth most all-time include Romo, Rodgers, Roethlisberger, and Russell Wilson—but #1 is Otto Graham (who retired in 1955), #2 is Sid Luckman (1950), and #3 is Norm Van Brocklin (1960). All three are championship-winning Hall of Famers. Indeed, “The Dutchman” Van Brocklin passed for a still-record 554 yards in a single game.

Yet none of them crack the top 50 in career pass completions, touchdowns, or yards.

So does this mean today’s quarterbacks, even those with video game numbers, are overrated and would struggle in earlier eras?

Hasselbeck fully acknowledges the way the game aims to accommodate QBs today but still thinks that, regardless of rules, the cream will always rise to the top: “There’s certain guys you watched and thought, ‘He’s got the arm, he’s got the physical skill set, the mindset.’ They’re passing the eye test. I think that those guys would be successful in any era. They were successful in their era because they were doing the things they needed to do. Peyton, Jim Kelly, Brett Favre, these guys are just physically really talented and loved the competition. I think they would have been able to adjust.”

Below, behold one of those guys who seem like they could have gotten it done at any time: two-time Super Bowl champ, 1971 Player of the Year, and Hall of Famer for the Cowboys, “Captain Comeback” Roger Staubach.