Benching a quarterback who rarely turned the ball over and usually won was a tough call.
And at times during the 49ers? 41-34 win over the Patriots, it looked like it was going to backfire.
But for all the discussion about the transition from veteran Alex Smith to Colin Kaepernick under center, the man taking snaps almost doesn?t matter with the way the 49ers play defense.
The league?s top-ranked defense bludgeoned the league?s top-ranked offense for the first 35 minutes or so, making the Patriots look like they were the ones on the road in adverse conditions. They pressured Tom Brady. They forced turnovers. They made Wes Welker disappear.
That?s not defense. That?s magic.
The Patriots entered the game averaging 36.3 points and 425.7 yards per game, and they showed why while erasing a four-touchdown deficit to tie the game in the fourth quarter.
But the 49ers showed some resilience, taking that shot and answering, stopping Tom Brady at a point where it almost seemed fated to become another chapter in his legacy.
The shots they were doling out all night had a cumulative toll on the Patriots, who looked gassed at the end. The 49ers improved to 10-3-1 and clinched a playoff berth, and they proved they can come up with a stop, which will be helpful when they?re playing people not named Tom Brady.
Here are five more things we learned during Sunday Night Football:
1. Kaepernick does some amazing things. That?s why 49ers coach Jim Harbaugh made the change.
But he might also do things that shorten the season.
Like many young quarterbacks, he will lock onto his first read, and he will throw interceptions. That?s fine, when he?s playing with a lead. But at some point in the next month (actually next week), he?ll see defenses which make him pay for it more than occasionally.
And Frank Gore?s not always going to be there to pick up his fumbled snaps and carry them for touchdowns. He needs to play a cleaner game if the 49ers want to make good this potential.
Kaepernick can make big plays, but there were some troubling signs in the midst of the win.
2. Take away the simple fact the 49ers changed quarterbacks in mid-stream.?They are a nightmare to prepare for because of the way they?re constantly changing personnel.
From the modified pistol formation they which caters to Kaepernick?s skills to empty backfields to traditional two-tight end, one-back sets, they present a constant challenge.
It?s hard to match up when you don?t know where people are going to be, and having tight ends as varied as Vernon Davis and Delanie Walker makes it that much harder.
3. Devin McCourty looks completely at home playing safety.
If the Patriots had a few more players in their secondary as good at their jobs, they would be much better off. Since converting from cornerback, he?s made plays, and they badly needed someone in the middle of the defense who could.
4. You know what else the Patriots could use? A running back with better hands.
Stevan Ridley is talented enough, but you wonder how many more chances he?ll get when turns it over twice in a significant game.
There?s a reason the Patriots have been a home for wayward veterans like Kevin Faulk and others over the years. Trust is important to coach Bill Belichick, and Ridley just burned a good share of his tonight.
5. At different points in the last few weeks, the Packers and 49ers have taken turns looking like they might be the best team in the league.
But both teams have a quiet problem that could loom large in the postseason, with kickers they can?t trust enough.
The Packers keep propping up Mason Crosby, but it?s telling some of the kicks the 49ers don?t let David Akers try any more.
He?s been shaky on all but the short ones all year, and you can easily see it changing play-calling in a close game.