Starlin Castro is the first Major League Baseball player in history to be born during the decade of Seinfeld, Nirvana, and the Macarena. And more than half a season after his debut, he remains the only player born in 1990 or later. (Think of that: he was born the day after Pretty Woman was released and a few months before Home Alone and Back to the Future Part III. Wow, I feel old.) He won't legally buy his first drink in the U.S. until at least the end of next season's Spring Training (look out, downtown Mesa!), but he's already played in 84 big league games.
That's usually a good sign for a guy's future.
A few weeks ago, in an article with probably the oddest of the dozens of Starlin-pun-based headlines to be used to date, FanGraphs' R.J. Anderson looked at the start to Castro's career as compared to other 20 year old shortstops, and found that he was in some awfully good company. At .295/.350/.418 and a 95 OPS+, once you remove the unreal should-have-been-MVP year by the young Alex Rodriguez in 1996, Castro was falling right in line with the best 20 year old shortstops in history.
That was sometime during the day on July 21. Since that night -- including a 4-for-5 yesterday afternoon (his fourth straight multi-hit game) -- Castro has hit .386/.409/.528. His line for the year stands at .320/.366/.450. He started too late to qualify for the batting title, but if he did, he'd be first among all shortstops in batting average (by almost thirty points), a pretty close third in OBP, and a less-close third in SLG. Baseball-Reference hasn't updated yet as I write this, but Castro's OPS+, the metric Anderson used, is around 110 (edit: close, 111), which would put him just behind inner-circle Hall of Famer Arky Vaughan for the best non-A-Rod twenty year old shortstop of all time.
Of course, Castro also has a .362 average on balls in play (BABIP). That's a number that's somewhere between really hard and impossible to sustain, and would be fifth in the Majors if Castro had enough plate appearances. Think of the best line-drive hitters in the league (e.g. Cabrera, Mauer, Hamilton), and their career BABIPs are probably no higher than .345 or so, and I don't have to tell you that Castro doesn't quite sting the ball the way Miggy and Hamilton do. But then, Castro's BABIP isn't absurdly high (like some other rookies I know); even if you adjust him down to, say, the .320 range (more in line with what you'd expect given his minor league numbers) and take off a couple extra base hits proportionately, Castro's line ends up looking something like .286/.332/.388 -- a lot less sexy than his current real line, but right around the current MLB average for shortstops (.264/.322/.372).
What that suggests to me is that in Starlin Castro, there's a very good chance that the Cubs have at least an average-hitting shortstop. And in being at least an average-hitting shortstop at age 20, there's at least a pretty good chance that Castro has a really, really stellar career ahead of him.
That assumes he can play shortstop -- the various advanced metrics are crazily divergent on him right now, to the point that he's a star by FanGraphs WAR and barely usable by Baseball-Reference WAR. But he's certainly athletic enough to handle it, and he's got a lot of time to cut down on his huge number of mistakes. Your friendly neighborhood Cubs fan has precious little to look forward to right now, but s/he ought to be awfully excited about watching Castro develop.