So it finally happened yesterday. The best player in the American League will be in Minneapolis for the next nine years. The deal is an eight-year extension, beginning in 2011, for a total of $184 million -- an average of $23 million per season (and rumors as of Sunday night suggest that he's actually just being paid $23 million in each year of the deal). This deal thus covers 2011-2018, Mauer's age 27 through 35 seasons. (It also includes a full no-trade clause, which I view as basically nothing at all; if the quality of his play erodes far enough to make it plausible that the Twins might wish to trade him, this contract will have made him untradeable, clause or no.)

There's already some analysis suggesting that the Twins might have overpaid a bit. I can see that, from a purely baseball-economic standpoint. A healthy Mauer will be worth that money and then some, but you might have expected the Twins to get a little more of a discount based on the significant risk that he'll suffer an injury (or several) and fall well short of that.

But the thing is, there was no reason for Mauer to give them any kind of discount for anything. Everyone who has paid any attention to this knew that the Twins absolutely needed to sign Mauer, both from public relations and baseball standpoints (large segments of the fan base are Mauer fans first and Twins fans second -- or close enough to that -- and it would be basically impossible to replace Mauer's production without spending a similarly huge pile of money). And it set up perfectly for both the Red Sox and Yankees to be interested; much is being made today of Mauer signing the fourth-richest contract ever, but I think it's noteworthy that just last offseason, the Yankees signed Mark Teixeira to a very similar deal -- also eight years, starting in his age 29 rather than age 28 season, and worth just $500,000 less per season. Mauer, even with the increased risk, is simply worth much more than Tex. If they'd give Tex $22.5 million for 8, they'd give Mauer, at a time when they need a catcher, much more than $23 million for 8.

So my preliminary take on it is that it's a good deal. They couldn't possibly have kept him for less, and they absolutely needed to keep him. That's enough for me.

The question is, what can they expect to get for their money? If Mauer plays another 138 games in 2010 (his total from 2009 and about what the various projection systems expect), he'll have played 837 games and caught approximately 620 of them. There's never really been a catcher quite like Mauer -- that's the thing with these elite players, it's hard to really find a comp -- but among catchers who had played at least 700 games through age 27 (there are only twenty-nine of them), here's a look at what some of the good-hitting ones did through age 27 and then from from 28-35:

As I said, nobody is all that comparable. Johnny Bench doesn't work, because by the time he was 28, his knees were much, much older than Mauer's will be, having caught something like 400 more games than Mauer will have (and he was also much more durable in his early years). Torre doesn't, because he was a poor catcher who had already switched full-time positions by age 28. Most of the other guys are poor comparisons just because they were never anywhere near the quality of player Mauer is. When Porter slipped a bit, he lost his starting job. Mauer could slip about as much and still be the best-hitting catcher in baseball. If Mauer's decline is in line with most of the guys' on here, his bat will still be good enough to be an asset -- even at 1B or DH, though in that case only a moderate one -- at ages 34 and 35.

Oh, and not pictured, but Ivan Rodriguez fails for the same reason as Bench. Odd career that guy has had. Mike Piazza hadn't played nearly enough games in the majors through age 27 to make this list, but from 28-35, he played 1053 games and had a 145 OPS+, missing significant time only once. The Twins would take that.

I think the three players most comparable to what Mauer through age 27 will look like are Yogi Berra, Bill Dickey and Mickey Cochrane (also numbers 1, 2 and 4 on the list of most similar players to Mauer through age 26, per Baseball-Reference). Mauer is a better hitter than any of them ever were, but again, they're simply the three most comparable to an incomparable player.

All three, through age 27, were very good-hitting catchers with some injury problems (Berra significantly less than Mauer, Dickey significantly more -- he'd missed 40+ games three times in the previous five years). All three exhibited very typical peak and decline phases for position players: they had some of their best years from age 28-32 (Berra won two MVPs in that stretch, Cochrane one, and Dickey had four top-six finishes), and declined after that. Berra declined rather slowly--his last great year came at 31, but he was generally very good through age 38. Dickey declined rather quickly, and Cochrane saw his career derailed by injuries; he had a great year (albeit in just 115 games) at age 32, but played only 71 total games in two more seasons after that.

Anything can happen, of course. Mauer could catch Jason Kendall's disease and suddenly become a below-average catcher. He could be forced to change positions and become a run-of-the-mill, just-pretty-good 1B. He could get hurt and never play again. Looking at the 29 players on that list, though, that kind of collapse seems unlikely. Catchers with about the mileage on them that Mauer will have on him by the end of 2010 -- even the injury-prone ones -- have tended to decline rather slowly across 28-35, not collapse, and are startlingly unlikely to suffer the kind of totally debilitating injury that people seem to be worried about. But anyway, anything can happen.

But I think what we and the Twins should expect to happen is for Mauer's career to follow a pattern similar to Berra's, Cochrane's and Dickey's. For the first four to five seasons, he should play at roughly his current level (which is better than his career 136 OPS+, but not his 2009; maybe a 145-150 OPS+ or so?). You can expect him to decline from there, and maybe even switch to another position somewhere in those final few years. From age 32 or 33 to 35, it's very unlikely he'll be earning his $23 million (unless there's another significant jump in player salaries, which is certainly possible). But if he stays fairly healthy for those first four or five, he'll be worth well over $23 million per year in those years, so they'll be very much in the black by the time he starts really declining. After that, if he declines gracefully like Berra, he'll be the best catcher of all time by about the same margin that Honus Wagner is the best shortstop of all time. If the end comes more quickly, like Cochrane's or Dickey's, he'll merely be somewhere in the top three.

It's entirely possible that they'll regret this deal. (Well, not regret: you don't "regret" paying taxes or obeying a subpoena. But it might be that they're paying more than market value for this thing they were required to buy.) But it's at least as possible that he'll ultimately be worth every single penny, or much more. Considering it's a deal they absolutely had to make at almost literally any price, I think they did about as well as they could possibly do.