There’s nothing quite as gripping as a post-apocalyptic adventure like “The Walking Dead,” “The Road,” “Y: The Last Man” or the 2021 San Francisco 49ers.

The 49ers reached the Super Bowl in the 2019 season but lived through an extinction-level injury cataclysm in 2020. They lost Pro Bowl pass rushers Dee Ford (neck, back) for 15 games and Nick Bosa (knee) for 14. The All-Pro cornerback Richard Sherman (calf) for 11, the All-Pro tight end George Kittle (knee, foot) for eight, their top wide receiver, Deebo Samuel, (foot, hamstring, Covid-19) for nine, plus various other starters on both sides of the ball for large chunks of the year.

Quarterback Jimmy Garoppolo (ankle) also missed 10 games; the fact that he does not receive top billing on their injury roll call is telling on a variety of levels.

According to Football Outsiders, the 49ers lost the equivalent of 166.6 games by starters to injuries, the second-highest total for an N.F.L. team over the past 20 years. That’s like losing 10 starters — nearly half of a 22-man offensive and defensive lineup — for an entire season. Covid-related absences increased “injury” rates across the league last year, but the 49ers still led the N.F.L. in players unavailable for health reasons by over 30 games. The team’s few survivors staggered to a 6-10 finish.

One year later, nearly all of the 49ers’ irreplaceable stars are healthy and back on the field, as is Garoppolo. The 49ers have started the 2021 season with narrow-but-still-convincing victories over the Detroit Lions and the Philadelphia Eagles. Samuel leads the N.F.L. with 282 receiving yards. Bosa has recorded three sacks. Kittle and Ford are once again playing at a high level. And Garoppolo has resumed his role as the person who sits behind the wheel of the self-driving car and makes sure that nothing malfunctions.

The 49ers are designed to be more disaster-proof than most teams, which made their 2020 collapse all the more frustrating. Shanahan’s offense emphasizes short passes to receivers who specialize in racing or rumbling for big gains after the catch; hence Garoppolo’s reputation as more of a desk clerk than a game manager. Running backs are also replaceable cogs in Shanahan’s machine. The 49ers could have operated effectively last season without some combination of Garoppolo, Kittle, Samuel, wide receiver Brandon Aiyuk, who was a 2020 first-round pick, and the top running backs Tevin Coleman and Raheem Mostert. In several games last season, including their 34-17 loss to the Green Bay Packers (this week’s opponent), they were without all of those players.

Similarly, the 49ers defensive line for 2020 was slated to feature five past first-round picks, including Bosa and Ford: Four starters and a spare tire in case of a flat. But Arik Armstead was the only 49ers lineman to start all 16 games. As a result, the team’s sack total dropped from 48 in 2019 to 30 last year. Under the circumstances, six wins were a remarkable feat for Shanahan and his staff.

Not all of the important figures from the 2019 Super Bowl campaign returned this year. Defensive coordinator Robert Saleh’s experience desperately assembling a semi-functional roster out of rookies and leftovers made him overwhelmingly qualified for the Jets’ head coaching job. Sherman was not re-signed after last season; the Tampa Bay Buccaneers are reportedly interested in adding him for their Super Bowl victory lap.

The 49ers have also not completely avoided injuries so far in 2021, though it’s naïve to think that any football team could. Cornerback Jason Verrett, who missed nearly all of the 2016 through 2019 seasons with a battery of injuries, tore his anterior cruciate ligament in Week 1. Verrett, oddly enough, was one of the team’s healthiest players last year. Mostert is also lost for the season, but San Francisco stocked up on reinforcements like the rookie Elijah Mitchell, who rushed for over 100 yards in the season opener.

Speaking of reinforcements, the 49ers traded up in the draft this spring to select North Dakota State quarterback Trey Lance with the third overall pick. Lance’s arrival suggested that Shanahan was seeking more than push-button management at the position, but also signaled the organization’s confidence that the team would get better simply by getting healthier. That has proved true so far.

A few changes aside, the 49ers are playing well with a starting lineup that looks a lot like their 2019 Super Bowl lineup/2020 injured reserve list, while Lance has been limited to gadget-play duties.

Football Outsiders’ research suggests that there’s a meaningful year-to-year correlation in a team’s injury rate. That’s bad news for the 49ers, who have finished in the top half of the league in games lost to injuries for eight straight seasons. The good news is that last season’s injury rate was so catastrophically high that some regression toward the N.F.L. average is nearly inevitable, according to the tenets of central tendency. Things simply must get better. If they don’t, at least the immensely talented Lance is equipped to survive a “Mad Max” scenario while the 49ers sift through the rubble and try to rebuild.

Despite their early-season wins, the 49ers appear to be a notch below contenders like the Buccaneers. The Packers game on Sunday will provide their only true test against a playoff-caliber opponent, before the team embarks on divisional matchups in the N.F.C. West, an unforgiving environment for a team with glaring weaknesses. Another 49ers Super Bowl run may have to wait until Lance is ready to replace Garoppolo and switch Shanahan’s offense out of autopilot.

But post-apocalyptic fiction is more about survival than success, perseverance than triumph. The 49ers have done a fine job so far of putting 2020 behind them and returning to as close to normal as possible. That doesn’t make them champions. But it certainly makes them relatable.