Jimmy Garoppolo is a franchise quarterback. But he might not be San Francisco’s franchise quarterback unless they sign him to a long term contract before the season ends.

The San Francisco 49ers gave up a high second round pick, but they didn’t “get” Jimmy Garoppolo in return. They rented him for 8 games, after which he becomes a free agent. To be specific, they got 3 things:

His services for half a year (in a lost season, with a dangerously bad offensive line); The right to franchise tag him; and First crack at signing him to a long-term deal.

Of these three, only the last is really worth anything, and if the Niners don’t take advantage of it, they’ve thrown away a top-35 draft pick. (To be precise, they will have traded a pick in the top five of the second round, for an end-of-the-third-round compensatory pick.)

The reason is simple: all the leverage in free agency lies with the quarterback. Decent QBs almost never reach free agency because they are so valuable. And any who do become free agents are vastly over-valued. Can anyone doubt this?

The top free agent last year was Mike Glennon, and he got $15 million a year. Mike GLENNON! Jay Cutler got $10 million coming back from retirement. Kirk Cousins, who’s not that great, is making $24 million thanks to the franchise tag, and he’ll make more next year (whether he’s tagged or not).

The craziest example is probably Brock “Lobster” Osweiler, who earned $21 million off of his 2016 contract as the top free agent. How did that work out? As Walter Football put it, “the Browns received a second-round pick just to pay Brock Osweiler $16 million to stay off the roster. That's how disappointing he was.” And yet, he got another deal for $775,000 this year, because he was a free agent, despite the well known fact that he’s terrible.

And the hunger for QBs is only getting worse, as every fan knows. Sports Illustrated lists seven teams “desperate” for QBs, and eight more shopping. If the Niners don’t nail down Garoppolo soon, they’ll be the eighth desperate team.

What QBs are potentially available to fill that need? Tyrod Taylor, AJ McCarron, Teddy Bridgewater, maybe a Sam Bradford, Kirk Cousins or (38-year-old) Drew Brees. They’ll all get $20 million plus per year, and Garoppolo (adjusting for age) is a better QB than any of them.

San Francisco has some attractive qualities — a gifted rookie coach-and-GM team, tons of money to spend, lots of draft picks. It’s a team on the way up. But it’s also a talent-thin losing team with a terrible offensive line that can get any QB killed. Other teams have attractive qualities too, like no income tax (in Florida), better media exposure (in LA and New York), or a legitimate No. 1 receiver (most teams).

The only leverage the Niners have is Garoppolo’s risk — the risk that he gets injured, or plays poorly, might convince his agent to settle for a little less money on a long-term deal now. But only four games remain, and that leverage is disappearing rapidly. Once those games are done, the Niners are just another team chasing this FA.

Every time a quarterback approaches free agency, his best move is holding out. If you franchise tag him, he gets a high, guaranteed salary — and starts all over as a free agent the next year. Unless you give him a top dollar, long-term contract with lots of guaranteed money — probably $25 million a year, $50 million guaranteed minimum — Garoppolo would be stupid NOT to hold out.

And if you’re going to give him that contract, you should do it now and eliminate the risk of losing him. It’s clear that he is somewhere between Alex Smith and Tom Brady in talent, and that’s plenty good for Shanahan to work with.

This is the time for the Niners to gamble. The upside is huge, and if he turns out badly, they’ll still be able to trade him to some other desperate team for at least a third round pick. Heck, the Eagles got a first for Sam Bradford.

There’s one huge risk that tagging Garoppolo creates — losing him to New England. Tom Brady is 40, and could easily get injured out, or just retire. He talks a big game about playing five more years and his statistics remain strong, but Brady exploded at his offensive coordinator in frustration recently and just missed two practices in a row with a nagging achilles injury.

It’s extremely unlikely he’ll retire this year, but I’d put it at 50-50 that Brady retires by the end of 2019. If the Niners tag Garoppolo for a year, and then tag him a second time a la Kirk Cousins, that’s two chances for Bill Belichick to offer Garoppolo the reins of football’s best team. A team with a legendary coach, tons of talent, a scheme that Garoppolo knows perfectly and has won with. It would be very hard to compete with that.