49ers’ season plows into the playoffs with Brock Purdy ready but still learning

He had helped close out a surreal and storybook regular season — another victory, another affirmation that he belongs on the big stage — and Brock Purdy’s work was done.

Well, it was almost done: As the San Francisco 49ers’ rookie quarterback sprinted toward the south end zone tunnel at Levi’s Stadium on Sunday afternoon, a 38-13 victory over the Arizona Cardinals completed and the NFC’s No. 2 playoff seed clinched, Purdy had one last throw to deliver.

Fans chanting his name, the seventh-round sensation barely broke stride while pulling a white towel from his uniform pants and, in a single motion, backhanding it into the risers behind the end zone. The 262nd and last pick of April’s NFL draft continued briskly on his path to the locker room and had no idea what happened next.

You might say that, in the wake of the Niners’ 10th consecutive victory — six of which have featured Purdy, the NFL’s latest out-of-nowhere sensation, directing the offense — some fans are going overboard.

In this case, two grown men lunged to try to catch Purdy’s towel and lost their balance in unison. One, wearing a Ronnie Lott throwback jersey inside a retro gold jacket with a matching “foam head,” tumbled over the railing and fell about seven feet onto his back . The other man took a similar spill and landed on the concrete about a yard away.

On a day when the Niners desperately wanted to avoid incurring injuries that could impact their Super Bowl hopes, Purdy — as I described the scene to him in the hallway outside the Niners’ locker room about 45 minutes later — abandoned his perpetually poised demeanor and dropped his jaw with alarmed concern.

“Are you serious?” Purdy asked. “Oooooh, man.”

Assured that both men seemed to have escaped major injury, aside from some obvious soreness, Purdy exhaled and asked, “They’re OK, though? That’s the important thing.”

If Purdy, like every NFL player, was especially attuned to the physical well-being of those around him Sunday — well, we get it. It had been an exceptionally emotional week in the NFL, in the wake of the horrifying cardiac event experienced by Buffalo Bills safety Damar Hamlin last Monday night and his seemingly miraculous improvement in the days that followed.

It made sense that Sunday’s resumption of NFL games carried overtones beyond the normal playoff-positioning anxiety. It all worked out in Santa Clara: Though there were choppy moments, including a trick play, 77-yard touchdown catch by A.J. Green that gave the Cardinals a 6-0 lead on the game’s second play from scrimmage, the NFC West champions handled their business.

It’s quite likely the Niners will have all of their key players for their playoff opener at Levi’s next Saturday against Seattle. And Purdy, head coach Kyle Shanahan’s Plan C at the sport’s most important position, will be slinging it with confidence as the football world tunes in to see how long this fairy tale will continue — and how happily ever after it might end.

“Purdy just does his thing,” cornerback Charvarius Ward said in a mostly relieved Niners locker room after the game. “I don’t see any reason why he can’t continue to do it, now that it’s getting real.”

It’s hard to remember that Purdy began the season as an afterthought, inactive on game day behind second-year starter Trey Lance and back-from-the-brink backup Jimmy Garoppolo . That changed when Lance suffered a season-ending ankle injury in Week 2, setting the stage for Jimmy G.’s unlikely and uplifting revival.

Then Garoppolo went down with a broken foot early in Week 13, necessitating Purdy’s ascent to QB1.

The Niners were hoping he could acquit himself adequately while relying on an abundance of established playmakers and an elite defense.

Instead, he has become the Brock Star.

On Sunday, Purdy (15 for 20, 178 yards, three touchdowns, no interceptions) boosted his passer rating to 107.3, which would have led the NFL if he’d had enough attempts to qualify. The Niners are averaging 33.5 points per game during that stretch, beginning with the Dolphins game in which Garoppolo got hurt in the first quarter, and, of course, haven’t lost.

To paraphrase Larry David, he’s been “Purdy, purdy good.”

No, Purdy hasn’t been perfect. Yet, he’s been so consistently good at reading defenses, getting the ball to the right place, buying time with his legs and fitting the ball into tight spots that it’s easy to believe the just-turned 23-year-old has already arrived.

Every so often, his rawness shows. Sunday, the Niners led 7-6 with 4:33 left in the first quarter when Purdy dropped back to pass on 3rd-and-12 from the Arizona 41, eyeing a first down or enough of a gain to summon kicker Robbie Gould for a field-goal attempt.

Purdy, pressured to the inside, spun and rolled to his left, where he was chased by Cardinals defensive end J.J. Watt. Playing the final game of his decorated 12-year career, the future Hall of Famer had already sacked Purdy once, and he would sack him again later. On this play, however, Watt gave futile chase as the young quarterback headed toward the left sideline.

Maybe I can get to the edge and buy some time , Purdy thought to himself.

The next thing he knew he was on the ground, having been dropped for a 17-yard sack by fast-closing, third-year inside linebacker Isaiah Simmons, who ran a 4.39-second 40-yard-dash at the 2020 NFL scouting combine.

“He’s a first-round pick, right?” Purdy asked me when I brought up the play after the game, referring to Simmons. I nodded.

“Yeah,” Purdy said, smiling. “I forgot about that. I’m so competitive that I feel like I tell myself, ‘Yeah, I can make it.’ But I definitely got humbled in that situation.”

Since showing up at his first rookie minicamp, Purdy hasn’t exactly been known for his humility in the 49ers’ locker room. His unruffled aura and strong sense of self stood out to fellow players and coaches, and when he began making plays on the practice field — first as the third-stringer in training camp, and later as the guy running the scout team in regular-season practices — his teammates embraced Purdy’s swagger.

Now, after a regular season that has included a masterful coaching job by Shanahan, it’s about to get real.

For the third time in four seasons, the Niners have a legitimate chance to win it all.

Three years ago Garoppolo and the Niners had a 10-point fourth-quarter lead against the Chiefs in Super Bowl LIV before it all fell apart.

Last season they had a 10-point fourth-quarter lead against the Rams in the NFC Championship Game before it all fell apart.

Purdy’s challenge is to keep it together, top that and get the Niners over that barrier.

If the Brock Star can get it done, Niners fans will be falling all over themselves to show him undying love — hopefully, without getting hurt in the process.

Michael Silver is a columnist for The San Francisco Chronicle. Email: mike.silver@sfchronicle.com Twitter: @MikeSilver