SANTA CLARA — Coach Kyle Shanahan made some big changes to the San Francisco defense this offseason in hopes of getting the 49ers back to the dominant level it had in 2021 and ’22.

New coordinator Nick Sorensen’s new unit gets its first real test on Monday night with a very challenging opponent as the Niners will go up against four-time MVP Aaron Rodgers and the New York Jets.

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Rodgers Poses Significant Challenge for 49ers

The 40-year-old Rodgers is coming off a torn Achilles tendon that ended his debut season with the Jets after just four plays, but the 49ers know well that he has both the mind and the arm to exploit any mistakes.

“My scouting report is he’s a legendary quarterback and you have to come with your ‘A’ game, because he’s the type where he’ll embarrass you,” said defensive end Leonard Floyd, who has lost eight of nine games against Rodgers when Floyd played in Chicago and Rodgers was in Green Bay.

“If you give him some momentum, he’s going to carry that momentum for the whole game. You just have to be on your Ps and Qs, because he’ll score every time if you let him.”

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49ers’ History Against Rodgers

The Niners have a long history going up against Rodgers when he was in Green Bay, facing him nine times in the regular season and four more in the playoffs.

Six of those games have come since Shanahan took over in 2017 with Rodgers winning three of four in the regular season and San Francisco taking both playoff games. But it’s never easy with Rodgers posting a 104.9 rating with 11 TDs and two interceptions in those six games.

“He’s always just had the savvy,” All-Pro linebacker Fred Warner said. “The ability to extend plays, to make the big plays, keep control of the game, obviously make the plays in the big-time moments. There’s nothing that you can just pinpoint and be like, ‘Hey, we got to stop him from doing this.’ You have to prepare for it all. We have a big test. … He does it all. He’s one of the greatest of all time for a reason.”

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Testing the New Defensive Approach

Going up against Rodgers will be a good test to see if the decision to fire Steve Wilks after one season as coordinator and promote Sorensen was the right one.

San Francisco had been one of the top defenses in two seasons under DeMeco Ryans but couldn’t reach that level under Wilks, who brought some changes that led to a disconnect between the front and the back of the defense.

The 49ers overcame those problems in the regular season to earn the top seed but were exposed in the playoffs. The run defense was gashed in wins against Green Bay and Detroit. San Francisco then allowed four straight scoring drives to end an overtime loss in the Super Bowl to Patrick Mahomes and the Kansas City Chiefs.

Shanahan promoted Sorensen to take over, counting on his familiarity with the style of play the team had in 2022 under Ryans to help the Niners return to their old ways. He also brought in Brandon Staley as an assistant to incorporate a few new wrinkles in coverage.

The front was overhauled with longtime staple Arik Armstead released in a salary cap move. Floyd was signed to be the bookend rusher across from Nick Bosa that had been missing in recent years, with Maliek Collins and Jordan Elliott set to share duties inside next to Javon Hargrave.

But the strength of the unit remains Bosa, Warner and cornerback Charvarius Ward, who is coming off his best season as a pro when he was a second-team All-Pro.

Ward believes San Francisco has its best secondary in his three seasons with the team thanks in part to the emergence of cornerback Deommodore Lenoir, who has excelled moving between the slot and the other outside spot.

But doing it against Rodgers, Garrett Wilson and the Jets won’t be easy.

“He’s a dog,” Ward said of Rodgers. “Real smart, veteran. He knows what we are running, probably because we are in the same defense that they (have) in New York, but Hall of Famer, one of the best players ever, best quarterback. We are going to have our hands full. But best against the best for sure.”

NOTES: DL Yetur Gross-Matos (knee) and LB Dee Winters (ankle) didn’t practice. … RB Christian McCaffrey (calf, Achilles) was limited. … Brandon Allen beat out Joshua Dobbs and will be the No. 2 QB to start the season. … The Niners named eight team captains: Warner, McCaffrey, Bosa, FB Kyle Juszczyk, TE George Kittle, QB Brock Purdy, WR Deebo Samuel, LT Trent Williams.