It turns out that NFL quarterbacks didn’t need an offseason’s-worth of practices, after all, to work on their timing with receivers or fine-tune the precision of the passing game. Across the league, many offenses have begun the new season far ahead of defenses, and quarterbacks have led the way.

Tom Brady’s career-best, 517-yard passing performance Monday night for the New England Patriots at Miami was the highlight of an opening weekend when nearly half the league’s starting quarterbacks surpassed 300 yards passing.

Three other quarterbacks — Carolina’s Cam Newton, Drew Brees of New Orleans and Miami’s Chad Henne — topped 400 passing yards. Another 10 passers threw for more than 300 yards. Together, the 14 of them set a record for any week of an NFL season, not merely an opening weekend, as did the 7,842 net passing yards league-wide (a figure adjusted to include negative yards for sacks).

It was not exactly what had been expected after an offseason without minicamps or organized team activities, thanks to the NFL lockout, and it might have been a preview of another season of record-setting offensive exploits.

“I’m definitely surprised,” said former NFL quarterback Tim Hasselbeck. “I’d talked to a bunch of quarterbacks and they’d all said, ‘It’s going to be brutal. We’re going to be seeing blitz looks that we haven’t seen before and have no plan for.’ You usually go to the first practice of training camp and the defense is way ahead of the offense, playing in the offensive backfield while the offense is trying to get situated.”

Brady faced blitzes Monday night from the Dolphins, yet passed for the fifth-most yards ever in an NFL game. Newton also withstood Arizona Cardinals blitzes Sunday as he passed for 422 yards, the most ever by a rookie in a season opener.

“I thought he was very impressive,” former Washington Redskins quarterback Joe Theismann said of Newton, the top overall selection in the NFL draft in April. “He showed a lot more accuracy than he’d shown previously [during the preseason].”

Newton’s passing display was part of a weekend when offenses largely did as they pleased and defenses mostly had no answers. With Henne throwing for 416 yards, the Dolphins and Patriots combined for 1,110 yards of total offense Monday night, the second most ever and the most in an NFL game in 61 years. Brady and Patriots wide receiver Wes Welker teamed to match the league record for the longest play from scrimmage with a 99-yard touchdown.

Returners also flourished, with three touchdowns on kickoff returns and five more on punt returns. The eight return scores were the most ever in a single weekend of NFL games.

But quarterbacks played the leading roles and they posted their big numbers even with four-time league most valuable player Peyton Manning out of the Indianapolis Colts’ lineup for the first time in 14 seasons. The season started last Thursday night with Green Bay’s Aaron Rodgers throwing three first-quarter touchdown passes, and slowed little from there.

“Is there one particular reason for it? Not that I’ve been able to see,” said Hasselbeck, now an NFL analyst for ESPN. “The Packers didn’t have all the offseason work but that back-shoulder throw from Aaron Rodgers to Greg Jennings, there’s just a feel for that.

“Maybe the [organized team activities] and that stuff really are overrated,” he added “. . . Maybe just training camp is enough.”

Rodgers certainly seems to believe that. After the Packers were questioned for not holding large-scale player-led workouts during the lockout, Rodgers made several mentions of that issue during his postgame news conference last Thursday.

“When you get into training camp and preseason, that [offseason] stuff does not have a major impact on the game,” Rodgers said. “For chemistry purposes maybe, getting the rookies up to speed. [But] I wasn’t worried about our guys.”

Without formal offseason practices usually overseen by coaches, Hasselbeck said, perhaps offensive coaches have streamlined their approaches and are sticking to the things their teams do best.

“Coaches are notorious for having all this time on their hands and doing project after project, complicating things to no end,” Hasselbeck said. “That’s all well and good, but then you have to communicate it and teach it. I’d be interested to see if they didn’t simplify things a little bit.”

Hasselbeck noted that some of the marquee passing performances came from quarterbacks such as Brady, Brees, Rodgers and San Diego’s Philip Rivers, who are well established in their offensive systems. But less celebrated quarterbacks also had big games, and their coaches were taking pass-first approaches.

Newton threw 37 passes in his NFL debut. The New York Jets, known for their run-first offense under Coach Rex Ryan, threw 44 passes and had 16 rushing attempts in Sunday night’s comeback triumph over the Dallas Cowboys.

The NFL simply is, more than ever, a passing league, largely because of rule changes over the past eight years that have restricted defensive backs’ ability to grab receivers down the field and made defenders increasingly wary of how they hit quarterbacks and wideouts.

“There’s a reason people are throwing the ball so much,” Hasselbeck said. “. . . It’s just kind of how it’s changed.”