When megadeals make sense

Great players never come for free. If you develop prospects into superstars, it requires years of waiting as you sift through your prospects and see which ones will in fact pan out. If you trade for superstars, you have to give up great talent in return. The fastest way to add a star, baseball's free-agent market, is also the most expensive avenue, requiring robber baron-like amounts of cash. This last option is why Boston's starting center fielder in 2013, Jacoby Ellsbury, will be wearing Yankee pinstripes in 2014.

As might be expected, Ellsbury had an impressive price tag, requiring a seven-year, $153 million contract to sign with the Yankees. While much has been made about Ellsbury not being a 40-homer guy and a player who has missed significant time because of injury over the past four years, there's a lot to like about this signing. Looking at the history of $100 million-plus free-agent signings, there are a number of general rules that separate good signings from bad signings, and Ellsbury's deal falls more into the former category.

Age always matters

Players require six full years of service time to hit free agency, so most stars have likely had their best seasons by that point. While the idea that players in their late 20s are just entering their peak years is an alluring scenario, it's not actually true. Even though modern medicine keeps more players in the game longer than 50 years ago, roughly two-thirds of regulars have their best season in the rearview mirror by the time they blow out a 30th birthday candle.

Many people were shocked by the contract Alex Rodriguez received when signing with Texas before the 2001 season, easily dwarfing every contract that came before and still ranking as the second-largest contract ever given. But they shouldn't have been. Megastars rarely hit the market at age 25 as A-Rod did, so he was also the most valuable commodity ever available.