Charles Rex Arbogast/Associated Press

While the football world spent much of the 2019 offseason obsessing over significant changes to the Green Bay Packers offense, the team—somewhat quietly by comparison—overhauled its defense as well.

That offense struggled to score points in new offensive-minded head coach Matt LaFleur's debut Thursday night against the Chicago Bears. But the revamped Green Bay D carried the Pack to a road victory by holding Chicago to just three points, 3.9 yards per play and a mere three third-down conversions.

Four of Green Bay's top defensive performers—linebackers Preston Smith and Za'Darius Smith, free safety Adrian Amos and strong safety Darnell Savage Jr.—weren't on the roster at the conclusion of the 2018 season.

Both Smiths and Amos were big-ticket free-agent additions from a formerly conservative front office that became uncharacteristically aggressive on the open market. Packers general manager Brian Gutekunst spent both of his 2019 first-round draft picks on defensive players, one of whom was Savage following a trade up.

The Maryland product had three tackles, a pass defensed and a quarterback hit, while the Smiths combined for 2.5 of Green Bay's five sacks, eight tackles and six quarterback hits. Amos—a former Bear who signed a four-year, $36 million contract in March—had five tackles and an end-zone interception that essentially iced the game.

That play might not have happened if not for the pressure generated up front by Preston Smith, reinforcing the idea that it was a group effort Thursday night.

Emerging 2018 incumbents Jaire Alexander, Kevin King and Kenny Clark also made significant impacts. Alexander provided shutdown coverage, mainly against speedy Bears wide receiver Taylor Gabriel. King and veteran slot cover man Tramon Williams held veteran Chicago wideout Allen Robinson in check (the former also had a sack), while Clark provided strong run defense and added half a sack.

To boot, fourth-year linebacker Blake Martinez had a sack while leading the team with seven total tackles.

Few expected the Packers defense to practically pitch a perfect game on the road against a talented, well-coached offense Thursday, but the strong performance shouldn't come as a surprise considering the capital (draft and financial) they've recently invested in that unit.

The Packers now have four defensive backs—Savage, Alexander, King and cornerback Josh Jackson—who were drafted in either Round 1 or 2 in the last 28 months, none of whom have turned 25. The 23-year-old Clark was also a first-round selection in 2016, and we're yet to even see much from high-potential 2019 first-round edge defender Rashan Gary.

Meanwhile, Gutekunst signed Smith, Smith and Amos to contracts worth a combined $154 million this offseason.

Za'Darius Smith, a 26-year-old 2015 fourth-round pick, improved markedly during his first four seasons with the Baltimore Ravens. His Baltimore tenure concluded with a breakout campaign that included 8.5 sacks despite the fact that he was on the field for just 67 percent of his team's defensive snaps. He was also a top-15 pass-rusher among edge defenders at Pro Football Focus.

The 26-year-old Preston Smith, meanwhile, had a pair of eight-sack seasons along with four interceptions and 13 passes defensed during his first four seasons with the Washington Redskins. Like Za'Darius, he's physically intimidating and durable.

Also 26, Amos was one of the best safeties in the game his last two seasons with the Bears. Per PFF's Mark Chichester, 47.1 percent of his targets in his first four seasons resulted in either a defensive stop or a forced incompletion, which is tied with Charles Woodson for the best rate since PFF started tracking that advanced statistic.

And thus a unit that surrendered too many points (25.0 per game) and forced too few turnovers (15, tied for 29th in the NFL) last season seemed destined to improve in 2019. But this is a hell of a leap, and it's encouraging that defensive coordinator Mike Pettine had them jelling from the jump. A lot of these guys have never played together, but you wouldn't know it based on Thursday's well-coordinated performance.

The whole thing looked and felt fresh.

Pettine was also in charge last year, but his defense was operating mainly with holdovers from the Dom Capers era. There was a staleness present, and a relatively old defense was hit harder by injuries than every defensive unit in football except the Philadelphia Eagles and Tampa Bay Buccaneers, according to Football Outsiders.

But then they became proactive, trading Ha Ha Clinton-Dix midseason and letting go of Nick Perry, Clay Matthews and Mike Daniels in the offseason.

Now, Williams is the only defensive player on the team who is older than 28.

It was a risky approach, but the early returns are extremely promising. Those results came in a hostile environment against the league's ninth-highest-scoring offense from 2018, likely still lacking chemistry and with limited contributions from Gary.

"I think we showed the league and folks watching that we're not just an offensive football team anymore," Rodgers told reporters after the game. "We've got a defense."

Rodgers undoubtedly knows he and his offensive cohorts will have to consistently generate more than 10 points, 3.7 yards per play, 213 total yards and two third-down conversions. But it provides some comfort to know your defense has your back during periods of transition, cold streaks or injury rashes.

When Rodgers and the offense had an off day at the same venue last December, Bears quarterback Mitchell Trubisky lit up the Green Bay defense as Chicago scored 10 fourth-quarter points in a 24-17 victory.

And that's been the norm. Thursday marked the first time in eight years the Packers won a game despite scoring fewer than 16 points. Dating back to the 2011 season, they had lost 21 consecutive games under those circumstances. And in 2017 and 2018 alone, they failed to win despite scoring 23-plus points on six occasions.

The new-look Green Bay offense is supposed to take some pressure off Rodgers, but it's already beginning to look as though the new-look defense can accomplish that task.

Brad Gagnon has covered the NFL for Bleacher Report since 2012.

Follow @Brad_Gagnon