It's by no means an immutable rule. But all else being equal, baseball's development curve breaks down like this: Players who break in and hold their own at a young age tend to be more likely to become stars over the long run, while late bloomers tend to see their success dry up quicker than you'd suspect.
A fourth-round pick by the Mets in 1999, just before his 18th birthday, Pagan finally broke into the big leagues with the Cubs seven years later. He was a part-time player in those first two years with Chicago, then again in 2008 upon his return to the Mets. Pagan was never much of a power hitter, having hit 19 homers in 648 career minor league games, and producing mostly singles and some doubles as a part-timer in the Show. He owned strong secondary skills, though, flashing above-average defense in center field, a solid batting eye, and good speed. In 2009, the first season in which he topped 200 plate appearances, Pagan put up career-best numbers in multiple categories, hitting .306/.350/.487 in 88 games.
He finally got his first clean shot at everyday (or nearly-everyday) playing time the next season, and had a big year: .290/.340/.425, with 37 steals, elite baserunning numbers, and defense that looked Gold Glove–ish by any and all advanced metrics; all told, he was a five-win player that year. To give you some idea of context, in 2012, only 34 position players produced more than the 4.0 Wins Above Replacement that Pagan delivered.
So did Pagan's employers err in relegating him to the minor leagues and then part-time duty for so long? Or was he truly a late bloomer?
The past two seasons have produced sketchier results, which makes you wonder. Plagued by injuries, Pagan hit just .262/.322/.372 in 123 games with the Mets in 2011. He rebounded in 2012, playing 154 games, hitting .288/.338/.440, and showing off his trademark speed and baserunning prowess. His defense has been another story. Baseball-Reference.com says Pagan cost his team a total of 14 runs over the past two seasons, per Defensive Runs Saved. Ultimate Zone Rating shows more inconsistent results, with Pagan costing his team 14 runs in 2011, then performing at around league average in 2012. Until we have detailed play-by-play-based defensive stats, we want to be careful jumping to huge conclusions, especially given how inconsistent defensive results can be when taken in single-year samples. But much of Pagan's historical value has been tied up in speed (it's helped his .318 career BABIP, for one thing) and defense.
The year-to-year variance, Pagan not playing every day until he was 29, relying on skill sets that are typically found in younger players, Pagan turning 32 next year it all makes you wonder. The center-field market got thinner when B.J. Upton signed with the Braves, Pagan might cost nearly half what Michael Bourn will eventually fetch (presumably from the Phillies), and he was a considerably better player in 2012 than, say, Shane Victorino. Given that the dollar figures only require Pagan to be about a two-win player (i.e., league average) over the life of the contract, this isn't exactly a huge financial stretch, either. But there's some risk that Pagan might regress into a player who isn't worthy of starting on a championship-caliber team. Maybe you overspend a little when you're going for your third World Series in four years. But with top center-field prospect Gary Brown climbing the minor-league ranks, and the opportunity cost associated with Buster Posey still lacking the kind of lifetime deal given to the likes of Ryan Braun and Evan Longoria, a four-year deal to lock up Pagan past age 35 looks a little risky.