49ers’ Brock Purdy is an NFL rarity, slinging it without a safety net

Working without a safety net early in your career isn’t highly recommended — not for tightrope walkers, not for rock climbers. Most jet airplanes require two pilots.

But for a young quarterback, flying solo is not a bad thing.

Brock Purdy doesn’t have a safety net. No one likes injuries in any workplace, but the broken bones in the ankle and foot of Trey Lance and Jimmy Garoppolo have been a blessing in disguise. Not for Lance or Garoppolo, of course. But it has worked for Purdy.

The 23-year-old has spent the past seven weeks looking straight ahead and not over his shoulder.

Purdy is the man. For now, and almost certainly for next year. And that puts him in a rare spot, heading into his biggest challenge yet: He is the San Francisco 49ers’ no-debate-about-it quarterback.

It is an elite position occupied by a select few like Kansas City’s Patrick Mahomes and Buffalo’s Josh Allen. Few rookies — even highly drafted ones — are given the keys to a Super Bowl-ready team and told, “It’s yours; try not to crash it, kid.”

And it is a rare position for a 49ers quarterback. You might have to go all the way back to Joe Montana in 1981 — and he was a third-year player then — to find an untested quarterback with such complete authority. Josh Johnson has as much chance of replacing Purdy as Guy Benjamin did of bumping Montana back then.

Even the great Montana was yanked from a playoff game in favor of Steve Young, in January 1988, in the third quarter against the Vikings. Once Young became the starter, he had to look over his shoulder — mostly at the shadow of Montana, but even at backup Steve Bono — if he struggled. Everyone’s favorite player is always and forever, the backup quarterback.

Dak Prescott — Purdy’s counterpart in the NFC divisional round Sunday — hasn’t had the same complete and total ownership of the Cowboys’ quarterback job that Purdy has had in the past seven weeks.

When Prescott missed five games this season and his backup, Cooper Rush, performed well in his absence, the “Is Dak the man?” debate began once again for the Cowboys.

On Sunday, both stellar defenses will plan on attacking the opposing quarterback. The Cowboys, who lead the league in takeaways with 33 (to the 49ers’ 30), think they will be able to rattle the 49ers’ rookie. The 49ers, who lead the league in turnover margin with plus-13 (to the Cowboys’ plus-10), think they will be able to unsettle Prescott, who led the league in interceptions with 15 in just 12 games.

The 49ers are the higher seed, the host and the favorite. Still, it seems there is more pressure on the often beleaguered quarterback of the Cowboys than on Purdy, who is still playing with house money. And the Cowboys certainly will be leery of a close game that could cause them to rely on their kicker for a game-winning field goal or extra point, after their horrendous kicking woes Monday against Tampa Bay.

The most intriguing stories in sports are unscripted, and Purdy falls into that category. His ascension to this lofty position was, of course, not by design. Most of the 49ers’ quarterback moves in the past two seasons haven’t been by design, but instead by happenstance (which makes the next chapter in the quarterback saga fascinating, though that’s a tale for another day).

A year ago, Lance was clearly not ready to take the keys to the car, so the 49ers stuck with Garoppolo, who took them to within one dropped 49ers interception of another trip to the Super Bowl. But Garoppolo had to look over his shoulder the entire season, knowing that his successor was standing on the sideline.

This year, it was “Trey’s team” until it abruptly wasn’t, when he broke his ankle in Week 2. But even during in his short starting stint, he had to contend with the looming presence of Garoppolo, back in the fold.

When Garoppolo broke his foot in the first quarter against Miami in early December, the job became Purdy’s. Period. No head on a swivel. No quick hook.

Purdy has proven he has the personality, drive and skill to succeed. But it certainly helps that he has the comfort and knowledge that he won’t be yanked over a mistake. That he, as Deebo Samuel noted last week, can call an unscheduled timeout and not feel the wrath of head coach Kyle Shanahan. (“That kind of shocked me,” Samuel said of the timeout Purdy called in his first start. “Kyle don’t play that. That showed me the type of guy he is.”)

Purdy’s learning curve has been accelerated by necessity. Now Shanahan can design a game plan completely for Purdy and not try to reserve some plays for another quarterback in case the kid gets wobbly. With a rookie quarterback, a lot of coaches might have to resort to a Plan B. The 49ers are all in on Plan P.

Purdy’s situation is reminiscent of Nick Foles and the 2017 Philadelphia Eagles. When Carson Wentz went down with a season-ending knee injury in Week 14, Foles became the starter for the final three regular-season games. Playing without a ton of pressure, he started all three playoff games and led the Eagles to a Super Bowl victory. But, unlike Purdy, Foles was in his sixth season and had played plenty of NFL football.

When these two storied franchises meet Sunday, both will be trying to move one step closer to a sixth Super Bowl trophy. They have been tied for third place on the all-time list with five Lombardi Trophies for 27 long seasons: The Cowboys last won after the ’95 season, the 49ers after ’94. If Purdy got to that title game, in his home state, he could become the youngest quarterback to win a Super Bowl.

Purdy can keep his eyes straight ahead, on that prize. He doesn’t need to look over his shoulder. And, to keep his sanity, he probably shouldn’t look down.

Ann Killion is a columnist for The San Francisco Chronicle. Email: akillion@sfchronicle.com Twitter: @annkillion