There have been plenty of signs that this year's baseball offseason is going to challenge our concept of what money means within the sport -- where a dollar, or a million of them, just suddenly doesn't seem to buy a whole lot -- but the clearest indication may have come Tuesday night, when rumor-gatherers led by Buster Olney tweeted that the price to acquire Marco Scutaro's services had risen to $24 million over three years. It wasn't clear who was willing to pay that price; Olney suggested the Giants were frontrunners (which makes sense), but Andrew Baggarly reported a few hours later that the Giants had offered a two-year deal with a vesting option for a third. Finally, Ken Rosenthal reported that Scutaro agreed to a three year, $20 million deal with the Giants, later confirmed.

Scutaro, who played exclusively second and third after coming to the Giants from Denver last July 27, is 37 years old; he'll turn 40 during or shortly after the 2015 World Series, the third year of that contract.

The thing about middle infielders at ages 37-39 is ... well, there are at least two things. The first is that there have historically been very few of them. Since 1947, only 25 second basemen and shortstops (having spent at least half their time in that span at either position) have played more than 162 combined games across their age 35-37 seasons. The second is that those players have tended to be not very good; those 25 have averaged just over three total wins in Baseball-Reference's version of wins above replacement (list here), so an average of about a win a year. Ozzie Smith and Joe Morgan were excellent, but Scutaro is neither of them, and Omar Vizquel was pretty good, but he was still playing a very solid shortstop, while Scutaro will likely be providing defense of a declining quality at second base.

It's hard to overstate just how small the pool of players with any level of success through the ages for which the Giants apparently just signed Scutaro. Derek Jeter and Jamey Carroll sit in the top 15 on both of the above lists, and both are just entering their age-39 years. Among second basemen, only seven have been worth around or above two wins at age 37 (Jeff Kent's 3.5 in 2006 is tops); only two at age 38 (led by Morgan's improbable 4.8); and just two at 39 (Morgan again at 3.0).

Scutaro, in 2012 and for four years or so before that, was a pretty useful player, and he'll likely be a useful one again in 2013. After that, it gets sketchy. It's worth noting that Carroll is a similarly useful player, a year-and-a-half older than Scutaro, and that the Twins signed him a year ago to a two-years-and-an-option deal that, even assuming the option is picked up or vests, tops out at a total value of $8.5 million, a bit more than 40 percent of what Scutaro will earn. Even considering the apparently inflated salaries we're seeing this offseason, that feels like a bit of an overpay, a premium for his brilliant but very-unlikely- to-be-repeated, 76-game burst with the Giants in 2012.

Even if you choose to expect next to nothing out of Scutaro at 39, you could look at the deal (regardless of its actual structure) as something like $10-$7-$3, which seems a downright reasonable expectation. And if the money is reasonable, the years scarcely matter; three years at $20 million is better than two at $20 million, clearly, on the chance he does have something left.

So by no means is the point here that the Giants made a bad deal. They didn't. But if history is any guide, there's an awfully good chance that the Giants will be looking -- or, at the least, their fans will be wishing -- for another new second baseman before the three years are through.