The San Francisco 49ers hosted Aaron Rodgers and the New York Jets on Monday night to close out Week 1 of the NFL season.

Surprisingly, star forward Christian McCaffrey was inactive as the current NFL Offensive Player of the Year is dealing with calf and Achilles tendon injuries.

It didn’t matter. Former undrafted rookie free agent Jordan Mason filled McCaffrey’s shoes, rushing for a career-high 147 yards on 28 attempts. San Francisco scored on eight straight possessions to win, 32-19.

Meanwhile, the 49ers defense held New York’s offense in check. Outside of a long drive in the first quarter and a broken coverage in the second half, this unit was dominant.

The reigning NFC champions opened their season in style. They still look to be the conference powerhouse. Here are five takeaways from the 13-point victory.

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No Christian McCaffrey, no problem

As mentioned above, Mason did his thing against the Jets on Monday night. Most of his damage was done between the tackles, with the 49ers offensive line winning all night long.

Rookie third-round pick Dominick Puni looked great as the starting guard in his regular season debut, dominating at the point of contact and being a huge anchor in the rushing attack.

There’s a reason he earned the starting job right away. According to Pro Football Focus, he had the fifth-best rating among 49ers players in Week 1.

San Francisco 49ers Red Zone Problems

Scoring on eight straight possessions is great. Seeing six of them end in field goals is not great. San Francisco scored two touchdowns on five red-zone opportunities.

The main culprits here were penalties combined with a horrific drop by Brandon Aiyuk in the end zone. Much was made of Aiyuk’s drop, as he had not practiced during training camp before signing a lucrative long-term contract.

It might not have hurt the 49ers in Week 1. But the competition is getting tougher. Problems in the red zone against teams like the Kansas City Chiefs, Dallas Cowboys, Green Bay Packers and Buffalo Bills would be a big problem. That’s especially true in close games.

San Francisco 49ers Cornerback Play Is Elite

We knew all about 49ers Pro Bowl cornerback Charvarius Ward ahead of Week 1 against the Jets. He led the NFL with 23 passes defensed and posted a paltry 64.5 QB rating when targeted last season.

Ward was up to his old tricks Monday night. In fact, Aaron Rodgers largely avoided his side of the field. The soon-to-be free agent gave up just 14 yards on five targets, proving himself to be a shut down guy.

The performance of underrated cornerback Deommodore Lenoir also stood out. He broke up a pass intended for Garrett Wilson that was eventually intercepted by linebacker Demetrius Flannigan-Fowles.

All told, Lenoir gave up 38 yards on six targets in the win. Even free-agent acquisition Isaac Yiadom had a key pass defended on fourth down in the final stanza. Depth can be an issue at cornerback. But the top three looked great in the season opener.

Brock Purdy was solid, but still needs to work on some things

Purdy completed 19 of 29 passes for 231 yards without a touchdown or an interception. It was a workmanlike performance for the reigning NFL MVP finalist against an elite Jets defense.

He did, however, leave some plays on the field. That included a high pass to George Kittle in the second quarter. It’s a pass that could very well have been intercepted. Purdy offered his thoughts on the 49ers’ offensive performance after the game.

“I thought there were a couple of things that we could all probably be a little bit better at, myself included,” Purdy said, via the 49ers’ official website. “Just the live speed and everybody being together, everything being together, shifts, motions, operations, going against man coverage, finding ways to get open and be on time. There’s just that sense of urgency that I think we can be a little bit better at.”

Purdy was clearly out of sync with the aforementioned Aiyuk, completing just 2 of 5 passes for 28 yards when targeting the All-Pro receiver. Lacking Christian McCaffrey’s dual-threat ability also played a role. It wasn’t a bad performance from Purdy. But he certainly proved he can play better.

49ers Run Defense Has Improved Vastly

Last season, opponents showed at times that they could match up against the 49ers, which is one of the reasons why San Francisco acquired defensive tackle Maliek Collins in a trade with the Houston Texans.

Collins played a big role in limiting Jets running back Breece Hall to 54 yards on 16 attempts. The 49ers also forced a fumble.

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Nick Bosa didn’t get sacked. But he also proved strong against the run. The same can be said for Javon Hargrave. Meanwhile, linebacker Fred Warner was the best player on the field Monday night. That included multiple assists on the ground.

If the 49ers can maintain this level of play against the run, their defense will be dominant. Add to that the cornerback play I mentioned above, and it becomes even more pronounced.