Let’s cut the crap. The 49ers just paid Brock Purdy like he’s the chosen one. Five years, $265 million. $182.6 million guaranteed. A $40 million signing bonus. That’s not “let’s see how this goes” money. That’s “you’re our guy, no questions asked” money.

But here’s the problem: what happens if he goes down, or worse, doesn’t live up to it? That’s where this gets dicey, because Kyle Shanahan’s system keeps making quarterbacks look like gods. And right now Mac Jones is proving the point better than anyone.

Mac got tossed into this offense and immediately looked like he’s been running it for a decade. He just lit up the Rams for 342 yards and two touchdowns, then helped the 49ers walk out with an overtime win. In his three starts he’s thrown for about 905 yards, six touchdowns, one pick, and is completing around 66 percent of his passes. Those aren’t “backup filling in” numbers. That’s starter production. That’s “keep the car moving and don’t crash it” quarterbacking, and he’s driving it like a Tesla on autopilot.

Here’s the real truth. Shanahan’s scheme is a machine. It’s not fragile. It’s built to get guys open, give quarterbacks easy reads, and scheme explosive plays into existence. That’s why San Francisco has consistently ranked as a top-five offense in advanced metrics. The system is so good that the line between “good quarterback” and “great quarterback” gets thin fast. When the machine hums like this, it feels like anyone with two working arms can step in and keep winning.

That doesn’t make Purdy bad. Far from it. But it does mean two things that 49ers fans better keep in the back of their heads.

1. The system hides cracks. Purdy’s numbers drop hard when he’s under pressure. And that matters, because you don’t hand out $182 million guaranteed for a quarterback who only looks elite when everything around him is perfect. If the line slips, if injuries hit, the system can only cover so much.

2. The money ties your hands. You cannot hand out this type of deal and then whiff. The guaranteed cash will squeeze the roster. If Purdy’s healthy and balling, it’s worth every penny. But if he misses time and guys like Mac Jones can still keep winning in the same system, the entire fan base is going to start asking if the 49ers just set themselves up for a giant cap headache.

So are they regretting it today? No. They’re 4-1 and the offense hasn’t skipped a beat. Mac Jones stepping in and delivering is proof that Shanahan has this thing running smoother than a cheat code. Right now the deal looks fine.

But what about three years from now? That’s where it gets tricky. It depends on:

• Whether they keep Purdy protected with an elite O-line and run game.
• Whether they can manage the cap around that massive guarantee.
• And whether Purdy can prove he’s more than a system quarterback, meaning he wins games when nothing else is going right.

That’s the whole story. Shanahan makes backups look competent. That takes the short-term pressure off the Purdy contract, but it also raises the bar on what Purdy has to do. If he’s just average within the system, history is going to roast this deal. If he grows into a quarterback who elevates everyone around him, then it’s the move that locks down their window.

The 49ers did what every team on the cusp does. They picked stability, locked up “their guy,” and shoved the chips into the middle. If they win a Super Bowl in the next two years, nobody will care about the price tag. If they fall short and Purdy looks replaceable, that guaranteed money will burn.

Here’s what you need to keep in your back pocket for the debate:

• Purdy’s $265M deal with $182.6M guaranteed.
• Mac Jones’ stat line in his three starts: 905 yards, 6 TDs, 1 INT, 66 percent completions, including 342 yards and 2 TDs vs the Rams.
• The 49ers’ consistent top-five offensive efficiency under Shanahan.
• Purdy’s steep dip under pressure.

Those four bullets tell the story loud and clear.