The Seattle Mariners just did a very curious thing: They signed free agent second baseman Robinson Cano to a massive 10-year, $240 million contract, tied for the third-largest in baseball history.

To be sure, Cano is a fantastic player, a possible Hall of Famer, and he was easily the best free agent on the market this offseason. Landing a player like that provides an immediate boost to any ball club.

But given the enormous price tag and Cano's age (31), the Mariners may have just blown up their future in a mad dash to win now at literally all costs.

The track record on these kinds of mega-deals for aging players is terrible. In recent years, we've seen Albert Pujols (10 years, $240 million), Prince Fielder (nine years, $214 million), and Josh Hamilton (five years, $125 million) break the bank in free agency.

And here's the WAR (wins above replacement) totals they posted in the past five years:

Pujols: 8.7, 7.0, 4.4, 3.7, 0.7

Fielder: 6.0, 2.7, 4.9, 4.8, 2.2

Hamilton: 1.2 (partial season), 8.4, 4.0, 4.2, 1.9

The trend: A sharp decrease in production. Pujols in particular has devolved from being one of the best players in history, a perennial MVP candidate, and an eater of planets into more or less an average first baseman a mere two years into his deal. He's still owed $212 million over the next eight years. Continue his regression trend and…yeah, not pretty.

Sure, Cano could flout the pattern. And his projected decline over the next decade would actually make his contract not too gross of an overpayment, in terms of market value.

But the Mariners have no room for error. They had a $74 million payroll last year, and they just committed to giving Cano roughly one-third that amount annually. While a team like the Yankees can afford to absorb a couple of horrendous signings here and there, a middle-market team like Seattle can't.

By agreeing to overpay Cano years down the road, the Mariners are gambling they'll reap an immediate return to justify the back-end of the deal. But the Mariners finished 20 games under .500 last year — 20! — and even with the Cano signing, they're hardly built for a playoff run.

Here's Fangraphs' Dave Cameron on that point:

Adding Cano certainly makes them better, but it probably pushes them up to being something like the ninth-best team in the AL; they are still clearly not anywhere near the level of the Red Sox, Tigers, A's, Rangers, or Rays, and still look to be comfortably behind the Royals, Indians, and Blue Jays. They're now comparable to the Orioles, or the Yankees before they spend any more money. Robinson Cano doesn't turn the Mariners into a good team. [Fangraphs]

The Mariners should have known better than to take this kind of eggs-in-one-basket approach given their intimate acquaintance with baseball's richest man, and noted centaur enthusiast, Alex Rodriguez.

In 2001, A-Rod left the M's to sign a then-record $252 million deal with Texas. The Mariners, bereft of Rodriguez's supreme talent, went on to have a miserable season the next year.

Ha ha, just kidding. The 2001 Mariners won 116 games, a 25-game improvement over their previous, A-Rod-having year.

The Rangers, meanwhile, went all-in for Rodriguez's services in hopes of bouncing back from a year in which they finished last in the division. The move didn't exactly pay off though, as they then posted three straight losing seasons. And with their purse strings tied by A-Rod's huge money-suck of a contract, they had no financial flexibility to address their many other needs.

Coincidentally, the Rangers' next winning season came in 2004 — the year after they dumped A-Rod on the Yankees.

The Yankees signed Rodriguez to an even bigger deal that is now one of the worst in baseball. And that horrible contract, combined with the Yankees' other massive outlays for unproductive, over-the-hill veterans, was the prime reason why the team collapsed into decrepitude and missed the playoffs last year.

For some perspective on how bad the Mariners deal looks, even the Yankees didn't even want to touch a $200 million — let alone a $240 million — commitment for Cano. Enough said.