…and here comes Anthony Rizzo! Let the celebrations begin! I mean the disappointment! Oh, the humanity!

In terms of “what is good for baseball,” I think the growing amount of hype around top prospects is a good thing. For one thing, it really is exciting to see new, young players. For another, it signals that the “casual fans” are getting more into prospects, which means they are getting more into the core of what it takes for a team to regularly win. It is a good thing when fans better understand the workings of baseball.

Of course, the hype also means that expectations grow ridiculously high. Sometimes (Bryce Harper, Mike Trout) players live up to the hype right away. Sometimes they never do (DeLOLmon Young), sometimes they take a while and few people realize they have actually become very good players (Alex Gordon). While scouting is key, especially when it comes to young, “unproven” players, basic statistical analytic principles still have relevance. This is clearly the case when one looks at at the reactions (both positive and negative) to some of last year’s hyped prospects who had big years and then followed up with a down season in 2012. Consider this a Prospect Panic Valium for a few cases.

Three brief case studies:

Dustin Ackley was Jack Zduriencik’s first big draft pick as Celebrity General Manager of the Mariners back in 2009. He was a top prospect in baseball — Baseball America had him #11 in 2010 and #12 in 2011. People had questions about how well his glove would transition to second base. He’s not wizard, but he seems to be coping out there. He had a nice major-league debut as a 23-year-old in 2011, showing a nice walk rate and a little pop in a tough ballpark for a .273/.348/.417 (117 wRC+).

This season has not gone so swimmingly. His walk and strikeout numbers are almost identical this year, but the power has dropped way back along with his BABIP. “Maybe this is who he is,” I read somewhere. Well, maybe. I will admit I had a hard time seeing from his Minor League stats how he was better than Jason Kipnis (although scouts apparently thought so — hey, scouting is hard). But you know what? He still might be. Yes, the most recent data is the “most relevant,” but those 376 plate appearances from 2011 didn’t just disappear, nor did his impressive 2011 season in the minors. Will he ever be a superstar? I do not know. But it seems crazy to just write him off as mediocre for one half of a bad season when he just came off of a good.

I wish I could find the piece from the off-season in which a “rival executive” says that the Royals could lock Eric Hosmer up long-term for 10 years and $100 million. (I heart super-credible sports journalism! But hey, those bloggers aren’t accountable to anyone…) It did happen. Hosmer initial forays in the minors in 2008 and 2009 were less than awesome, and during 2009 it turned out he needed LASIK surgery. In 2010 in the minors things changed, as he destroyed the ball on two levels. He blew scouts away all year and into 2011 Spring Training. I’m a nobody, and at Spring Training 2011 executives from multiple other clubs were offering up unsolicited raves about Hosmer. After a brief sojourn in AAA, he came up in Kansas City, and while .293/.334/.465 (114 wRC+) may not be mind-blowing on its own for a first baseman, it surely was for a 21-year-old, especially when you look at the list of players who have done similar things. That is why the 10/100 deals and Joey Votto comparisons started to be made.

If people had looked more closely, they might have noticed that the Votto comparison did not quite work, but there was no doubt that the Hosmer hype was understandable, if overstated. Fast forward to this season: Hosmer is currently hitting .221/.290/.373. Let’s put it this way: Jeff Francoeur has returned to being Jeff Francoeur (I’m as surprised as you guys!), and yet no one is really raising a stink about Hosmer hitting behind him. Obviously, Hosmer is now a total bust.

Yeah, Hosmer was over-hyped after last season. I will agree that “luck” is probably not a sufficient explanation for his .222 BABIP so far this season. But hey: we are still just 290 plate appearances of horror this season compared to 563 excellent ones last year. He is not turning 23 until October. That alone should calm people down, even without noting that his plate discipline has improved (better walk and strikeout rates). The 10/100 talk was silly last year, but 290 plate appearances is still barely enough to move the needle. They certainly do not cancel out near-universal raves from scouts and a much larger and more impressive sample at age 21.

Finally, we come to the player who indirectly inspired this post via angry questions about his 2012 performance in my weekly chat at FanGraphs: Desmond Jennings.

Coming in to 2011, fantasy owners knew two things about Desmond Jennings: a) he stole tons of bases, and b) he seemingly got hurt all the time. When he finally came up (remember when the critics said the Rays were going to cost themselves a playoff spot by gaming Jennings’ and Matt Moore’s service time? That was awesome.), he did more than just steal bases. In only 287 plate appearances, he slugged 10 home runs and finished the season with a nice .259/.356/.449 (131 wRC+) line, throwing in 20 stolen bases to boot. That was more than people expected… and more than people should have expected.

Jennings got hurt early this year, and now is drawing the ire of fantasy owners over his .240/.302/.347 (90 wRC+) line. Now, look, I think “he’s getting over his injury” is often a lame excuse, and I am not using that here. But, I mean, it has still only been 215 plate appearances. That is pretty close to meaningless, statistically speaking. In The Book, we find out that at 220 plate appearances, one regresses a player’s offensive performance as measured by wOBA midway between his observed performance and the average for his population. That’s a fancy-schmansy way of saying that If this year was everything we knew about Jennings, we’d estimate (with a lot of uncertainty) that he was pretty much a league-average hitter.

As in the case of Hosmer, we have a case of over hype based on an even smaller sample. Moreover, in Jennings case, people were seduced by power number out of line with what he had done in the minors, and it should have been obvious those would come down. This is different from Brett Lawrie, who changed his swing in response to coaches’ advice in 2011 and has continued his power surge into 2012. Oh, wait. But the main thing to keep in mind, once again, is that Jennings prior performance in the minors and last year in the majors still dwarf the small sample from this season.

Now, this may sound like the same old “small sample” stuff you get from the nerds all the time, and in a way that is true. But it seems necessary in these cases because with young players, it seems that the overall small sample of data we have for these playesr gives people “permission” to over-react to each shift in performance. It is fun and good as a fan to get excited about prospects. But if we are going to warn people not to buy into the hype, we should also caution against falling head-over-heels in disappointment over the 200 plate appearances, even if that is one-third or one-half of a player’s Major League sample.