The San Francisco 49ers traded Christian McCaffrey to see what a supercharged sports car looks like in Kyle Shanahan’s offense. The results were amazing.

But the hallmark of Shanahan’s offense, going back to Kyle’s father, Mike, and his days with the Denver Broncos, is taking running backs that no one else wanted and having a ton of success with them. Backs like Jordan Mason.

With McCaffrey surprisingly inactive Monday night with a calf injury and Eli Mitchell on the injured list, this was Mason’s chance to play a big role. And against one of the NFL’s best defenses, the undrafted free agent had the best game of his career in his first NFL start.

Mason had 147 yards and a touchdown on 28 carries, leading the 49ers to a surprising 32-19 win over the New York Jets on Monday night.

Mason, of course, didn’t carry the 49ers. Deebo Samuel Sr. split the backfield duties and had a touchdown. George Kittle made plays. Brock Purdy started slow but got hot once he settled in. Purdy hit fullback Kyle Juszczyk for a 34-yard catch that set up a touchdown for Mason early in the third quarter that effectively put the Jets out of the game. The 49ers defense is one of the best in the NFL and it showed. But Mason lived up to what every backup dreams of, getting his chance and shining when the spotlight was on him.

The 49ers’ offense looked better than ever, scoring on eight consecutive possessions after a punt to start the game. San Francisco’s defense spoiled Aaron Rodgers’ return to the lineup after missing most of last season with a torn Achilles tendon. Rodgers completed 13 of 21 passes for 167 yards, one touchdown and one interception.

The 49ers are clearly still better with McCaffrey. But the 49ers are the rare team that can put an undrafted free agent in place of the reigning NFL Offensive Player of the Year and look just as good on offense.

49ers beat the Jets

The night didn’t start out too badly for the Jets. Rodgers, playing in just his second game with New York and his first that lasted more than four snaps, led an impressive touchdown drive late in the first quarter. Breece Hall scored near the end and the Jets led 7-3.

New York’s defense looked good early on. The Jets put pressure on Purdy and stopped the run. After a fumble by Hall in Jets territory, New York quickly got a three-and-out and the 49ers settled for a field goal. It looked at this point as if the 49ers would struggle to move the ball all night against a deep and impressive defense.

But the 49ers figured it out. They gave Purdy some time, and he found the open receiver, as he usually does. Even with Brandon Aiyuk looking rusty after sitting out the entire month of August seeking a new contract, Samuel, Kittle and Juwan Johnson made plays.

Mason scored to give the 49ers a 23-7 lead in the third quarter, and then Rodgers made his first big mistake. He hesitated under pressure, then tried to squeeze a pass to Garrett Wilson. But 49ers cornerback Deommodore Lenoir had great coverage, tipped the pass, and it was intercepted by linebacker Demetrius Flannigan-Fowles. It was just past the halfway point of the third quarter, but the game looked over. It’s not like the 49ers defense was going to let that happen.

The season wasn’t even three-quarters old for the 49ers, but they looked like one of the best teams in football again. Even without McCaffrey, one of the best players in the NFL.

Jets still have work to do

Monday night’s performance must have been discouraging for the Jets. They entered the season with renewed optimism with Rodgers back, and it didn’t appear they were at the 49ers’ level. But it’s only the first week of the season. Rodgers in particular should improve as he shakes off some of the rust. After all, he’s played just four regular-season snaps since January 2023. New York should finish this season just fine.

The way the Jets were buried probably said more about the 49ers. The Jets will finish with one of the best defenses in the NFL, but the 49ers were able to move them around the line, creating holes for Mason, and there always seemed to be a receiver open when Purdy needed them. The 49ers defense is one of the best in the NFL, and that’s a big reason why Rodgers’ first game back from injury was so quiet.

We’ll see how the Jets bounce back. We know what to expect from the 49ers by now. They’re a Super Bowl contender again. Imagine how much better they’ll look with McCaffrey back in the lineup.