Whatever contract Alex Rodriguez signs this offseason is going to set all kinds of records- it's likely going to be the largest in the history of American sports, and would be his second $250MM+ contract. But I think the most amazing part of all this is the potential that some team is going to sign him for 10 years.
Initially, this doesn't seem all that absurd, probably because he's already signed a contract of that length. But last time he was 25; now, he's 32.
Here are the fourteen largest contracts in MLB history, along with the age each player was (or will be) in the last year of the deal:
(Soriano will be making $18MM in his age 38 season, which is fantastic. And Mike Hampton is still on Colorado's books next year. Data from Wikipedia and double-checked at Cot's Contract because, well, it's Wikipedia.)
The Brown contract is the outlier here; I'm not really sure how giving a 34-year old pitcher a seven year deal was a good idea, but that's OK.
Beyond that, nobody else on this list was signed past their age 38 season; the "end year" of 10 of these 14 contracts is between age 34 and 37 seasons.
If Boras somehow gets him ten years, Rodriguez's contract will run through his age 41 season. An eight year contract would take him through age 39, which is still somewhat insane, although less so.
It's difficult enough to know if A-Rod will be worth $30MM+ in 2008, but in 2017? That doesn't seem like an bet anyone should be willing to make, even in a world where closers are making $15MM when they're 40. And there is absolutely no precedent for anyone making such a long-term commitment to a player that's already 32.
Over at BBTF, a couple guys had an interesting idea. They said they think Boras will get Rodriguez something around 8 years, $270 million. But then he'll add on ridiculous team options for 2016 and 2017. This way, all the headlines will be "Rodriguez signs $370MM Contract", and Boras' $350MM demands will seem more reasonable, even if there was never a chance he was going to get that much guaranteed money.