It matters that Patrick Mahomes is spectacularly talented, of course. Might matter just as much that he is almost always available for the Kansas City Chiefs.
Same goes for the Philadelphia Eagles and Jalen Hurts.
Those are big reasons the Chiefs and Eagles will meet in the Super Bowl — with AP NFL MVP and Offensive Player of the Year finalists Mahomes and Hurts taking the snaps — on Sunday in Glendale, Arizona. Sure, the San Francisco 49ers nearly managed to make it all the way to the championship game with a last-pick-of-the-draft rookie bumped all the way up to starter from No. 3 on the depth chart because of injuries to others. But then Brock Purdy hurt his elbow in the NFC title game at Philadelphia, leaving the Niners to try to rely on journeyman Josh Johnson, until he got a concussion ... meaning Purdy needed to go back in ... despite being unable to throw.
"That," 49ers coach Kyle Shanahan said, "was kind of just hard to stomach."
This season revealed, like never before, a glaring amount of instability at quarterback in the NFL, whether because of injury — the reason for nearly half of all changes during the regular season, according to an AP analysis — or poor performance. A total of 68 QBs started at least one game, an average of more than two per team and a record for a non-strike year.
What's more: 13 clubs, another high, needed to use at least three starters at the most important position in this, or any, sport. Some even turned to four — with the Arizona Cardinals using that many starting quarterbacks in a span of just four weeks.
Quarterback shuffling can go a long way toward altering a team's trajectory, as the Jets, Titans and Panthers found out on their way to missing the playoffs. The Dolphins made the postseason despite losing Tua Tagovailoa to a series of concussions, then had backup Teddy Bridgewater dislocate his pinky, leaving them with third-string rookie Skylar Thompson and his 18-for-45, two-interception performance in their wild-card elimination.
"When you, as a defender, see a guy at quarterback who has not played a lot, you are going to lick your chops and you assume he's not going to be in rhythm and you assume he's not going to be ready to go," Hall of Fame defensive back Ronnie Lott said. "Our coach, Bill Walsh, basically said, ‘Hey, Ronnie, a team's only as good as the backup quarterback, because if the backup quarterback can't come in and do the things he needs to be able to do, a team is going to be in trouble.'"
And keeping the starter upright is almost always needed for success.
The top five regular-season teams in the AFC, including the Chiefs, had their No. 1 QB available for every regular-season game (and when Mahomes did leave a playoff game with a bad ankle, Chad Henne came in and delivered, leading a 98-yard TD drive in what turned out to be a seven-point victory).
In all, nine of the 14 participants in the postseason never had to turn to a backup QB to start.
The Eagles came close: Hurts missed two games with a bad shoulder; Philadelphia went 0-2 with Gardner Minshew in his place.
Seems obvious: Having your preferred QB1 available week after week makes your offense more likely to succeed. And that makes your team more likely to win.
Consider that the passer rating for QBs slated to be starters was about 10 points higher than for replacements. Or look at the Jacksonville Jaguars and Trevor Lawrence: He stuck around for 17 games and closed with five wins in a row — three against the QB-troubled Jets or Titans — to earn a playoff spot.
"It's certainly key, just because everybody continues to gel. You get the chemistry together. The receivers know, ‘If I run this route on this step, the ball is going to be thrown to this point, just because we've done it a million times,'" Jaguars offensive coordinator Press Taylor said. "You can understand how (an injury absence) throws guys off."
Backup quarterbacks generally get zero practice time with the rest of the first-team offense during the season, so when the top choice at that spot is removed, there can be growing pains. Purdy was an exception, of course, and there have been others.
"Sometimes when a quarterback goes down," Cowboys guard Zack Martin said, "there's kind of a sense of panic in the locker room and on the team, like, ‘What are we going to do?'"
Some of the season's dominant story lines involved sidelined QBs, from Miami's Tagovailoa to Baltimore's Lamar Jackson to the reigning Super Bowl champion Rams' Matthew Stafford, or efforts via officiating to protect them, whether the outcry among defenders over roughing-the-passer calls or the 15-yard penalty on Bengals defensive end Joseph Ossai for shoving an out-of-bounds Mahomes that helped KC get into position for the winning field goal in the AFC title game.
Lowering the number of quarterback injuries is "obviously a major priority for us," said Troy Vincent, the NFL's executive vice president of football operations. "It's critical that we examine ... where they're coming from. Are they legal hits? Are they in the pocket? Out of the pocket?"
Increased impatience when it comes to wins and losses accounts for some of the switching — the same sort of itchiness that leads to first-year coaches getting fired.
But it seems to always come back to injuries.
One potential cause: Rushing attempts by signal-callers reached a record high (2,309) and were also at their most per game, up 47% from 2012. That increases the opportunities to get hurt. Another: The 1,297 total sacks around the NFL were the third most ever and the average of 4.8 per game was the third-highest over the last nine years. (As an aside, Mahomes and Hurts might want to watch out on Super Sunday: The Eagles ranked No. 1, the Chiefs No. 2, in sacks.)
It's certainly possible, or at least plausible, that whatever the NFL does to try to keep quarterbacks safe isn't working — and, truly, can't work.
"At this point, you're hoping," Lott said, "your quarterback can withstand the pounding."
The 49ers under Shanahan are Exhibit A: The team kept one quarterback healthy only once in his six seasons — in 2019, when they just so happened to reach the Super Bowl.
They went through at least three starters in four of the last six seasons; this time, Trey Lance broke an ankle while running in Week 2 and Jimmy Garoppolo broke his foot on a sack in Week 13.
"It's awesome," star tight end George Kittle said sarcastically. "It's an experience. I just have a plethora of quarterbacks to choose from."
The rash of injuries for the 49ers and others raises the question of whether the league should bring back some form of the 1991-2010 rule that let teams have a third QB in uniform who would not count against the game-day roster limit and would be available in an emergency.
"We were scared to death when that rule ended, but you kind of forget about it, since you just don't see anyone have to go through it," Shanahan said. "But then you get reminded of how quickly a football game is over once that happens."
The NFL's Vincent said there have been "multiple discussions" about restoring the third quarterback rule, and the general manager advisory committee "is considering" putting it before the full membership.
"What you don't want is Christian McCaffrey playing quarterback," Lott said, referring to the 49ers' do-everything running back. "With all due respect — he's a hell of an athlete, but he needs to be where he is most effective, and that is running and catching the ball, not playing quarterback."
AP Pro Football Writers Schuyler Dixon, Mark Long and Teresa M. Walker, and AP Sports Writers Dave Skretta and John Wawrow contributed to this report.