I've been fawning over Starlin Castro for a while now. Let's establish this now. Not only am I a complete sucker for quality shortstops, but he's also easily the best young player to show up at Wrigley Field in years while wearing a Cubs uniform. Watching top prospect after top prospect struggle upon reaching Chicago was like pouring salt on some very old wounds (Oh, your past sucked, huh? Well guess what? Your future's gonna suck, too!!). Castro's breakout rookie season from last year was like someone walking into the room and asking, "Why the hell are you pouring salt on that guy's wound? He's just laying there. We should help him."
His emergence over the past year has pretty much been a dream come true for both Cubs fans and headline writers alike- and as someone who always roots for the Cubs and sometimes writes headlines, I can already admit that Castro's probably my favorite player on the club. But there's a bigger question begging to be asked here, and that's whether Starlin Castro has already established himself as a legit star player.
When you think about what constitutes a star, at least in terms of WAR, you'd probably say something in the 3+ range. Or at least, 3 WAR would seem to be the bare minimum for a player to qualify as a star. There are certainly a large number of players with star reputations that generally see their WAR marks in the 3-4 range. Torii Hunter, for example, has fallen in the 3-4 WAR range in three of the past four seasons, falling below that range once. But ideally you'd probably want your true stars to be in the 4+ WAR range, with peak seasons around 5-7 WAR.
So where exactly does Castro fall, at least for this season? Let's start by assuming that he'll get roughly 650 plate appearances this season; that number could be slightly higher if he stays healthy and leads off all year, but we'll round down some and stick with 650 to account for possible injuries and the like. Projections seem to have the shortstop in the .295/.345/.410 range offensively for this season. He's had a monster start, though, and I think it's fair to project a little more batting average and power than the systems say. So let's say that he's a .300/.355/.425 hitter this season- not too far off from what he did in 2010. That's good for a roughly .345-.350 wOBA, with one specific calculation coming out to .347. Using a .330 league average wOBA (last year's was .321, but it should go up somewhat), that wOBA comes out to about 9.8 runs above average per 650 plate appearances.
So offensively, we have a +10 RAA hitter over the course of 650 PA. But Castro should bring a good deal of value defensively as well. Castro graded out as slightly below-average according to UZR and ADR last season. When you watch him play, he certainly makes some mental mistakes on the fields and isn't that polished, but the tools are there. He's only 21, so we'll say that he's roughly average defensively at shortstop this season.
Let's put that all together, now. A +10 hitter that plays average defense at shortstop over the course of 650 plate appearances, with a replacement value of 21.7 and a positional value of +6.5, comes out to roughly 38 runs above replacement. That's good for about 3.8 WAR, right at the high end of the initial star range that we discussed before. So even as a 21-year-old, we're looking at a star-quality player in Castro. Given what we've seen from other players that have been this good at such a young age, there should be some serious optimism surrounding the young shortstop.
Castro may not do anything spectacularly yet, which is likely why players like Buster Posey, Jason Heyward and Mike Stanton outshine him so much. He's not a brilliant defender, he doesn't have huge power and he doesn't work the count like he's got all day. But he does practically everything well, with a solid glove, good power for the position, and impressive contact skills that help to make up for the lack of patience. And given his build and tool set, most people expect more power to come, and additional experience should help him to improve his approach at the plate as well.
When we talk about the game's future stars, naming the big guys like Heyward, Posey, Stanton and Carlos Santana, there's absolutely no reason why we shouldn't be mentioning Starlin as well. The Cubs already have a star in Mr. Castro; what's exciting is that he could shine even brighter.