By Simon Evans

MIAMI | Tue Nov 20, 2012 9:03pm EST

(Reuters) - It is no surprise to see elite NFL quarterbacks such as Tom Brady and Drew Brees racking up big numbers in yardage this season but what is increasingly noticeable is the number of less accomplished quarterbacks joining them.

Three quarterbacks have already passed the 3,000 yard mark this season, Brees, Atlanta's Matt Ryan and Oakland's Carson Palmer, and plenty more are poised to join them.

More significantly, eight quarterbacks are averaging over 290 yards per game, including Indianapolis Colts rookie Andrew Luck (296.5), Detroit's Matthew Stafford (298.8) and the oft-criticized Dallas Cowboys signal caller Tony Romo, who has passed for 2,916 yards from 10 games.

Three years ago only two quarterbacks, Brees and Houston's Matt Schaub, averaged more than 290 per game, and five seasons back, only New England's Brady managed it.

Admittedly, the bad weather winter games have yet to come and they can push down averages but there are plenty of other signs that quarterbacks are gaining more and more yards in the modern NFL.

Breaking 500 yards in a single game used to be one of the rarest of achievements. Only two players managed it in the entire 1990s, yet two players have done it already this season.

Schaub, not even ranked in the top ten quarterbacks in the league, did it with 527 yards against Jacksonville on Sunday while Eli Manning threw 510 for the New York Giants in September.

Last season, Brady and Stafford both threw over 500 in a single game.

One of the longest standing records in the league, Johnny Unitas' record of scoring a touchdown in 47 consecutive NFL games, had stood for 52 years but Brees broke it this season and has taken it to 53 games so far. Brady is also closing in on the old record, throwing touchdown passes in each of his last 42 games.

So, why are quarterbacks producing significantly better performances, in numerical terms at least, than five, ten or 20 years ago?

Former Washington Redskins quarterback Joe Theismann, a Super Bowl winner in 1982, believes it is a combination of factors.

He said there was a great new generation, increased protection given to quarterbacks and the evolution of game plans away from the running game and towards heavily pass-centered strategies with offenses that spread the field.

"I think it started in the late 1990's, certainly when Peyton Manning, Tom Brady and Drew Brees came into the league but it has exploded even more in the last three years," he told Reuters.

The shotgun formation, with the quarterback stood around five yards back from the line of scrimmage and spread formations with receivers spread widely, has helped lead the dominance of the pass.

"You are very limited in the runs you can run from there and so you basically end up throwing the football all over the park. Let me put it this way, I'm envious," he said.

"It's much easier to throw the ball than it was five years ago. You spread a defense out and figure out where people are, where they are coming from, who to block, if you put four receivers across the field.

"You can tell what they want to do. Do they want to go man-to-man or zone? You get a much quicker read of what the defense is trying to do to you.

Theismann also noted teams no longer tried to protect their lead by running the ball, instead racking up the passing yardage.

"It used to be that 'you throw the football to get a lead and run the football to protect it'," he said.

"That was an accepted theory. Now you throw the ball to get the lead and keep throwing to increase it."

Theismann said the new generation of quarterbacks could be even better than the game's current standard-bearers because of their versatility.

"With guys like Cam Newton, Josh Freeman, Robert Griffin III and Andrew Luck, those four guys if you are able to play-action with their ability to run the football what does a defense do?," said Theismann.

"Do you protect against the run? Do you protect against the running quarterback and commit your linebackers? And if you do you have got receivers running wide-open. Being a defensive coordinator today will get you bald or gray hair in a hurry".

(Reporting by Simon Evans; Editing by Julian Linden)