Prospect Bonanza

Top_MLB_prospect_debuts_2015Data via Baseball America and the Baseball-Reference Play Index

As many baseball writers have noted, 2015 is a banner year for top prospects. After last weekend’s promotions of Byron Buxton and Francisco Lindor, nine of Baseball America’s preseason top 20 prospects have debuted this year, including each of the top four (Kris Bryant, Buxton, Addison Russell, Carlos Correa). That number is tied for the fourth-highest since BA started ranking prospects in 1990 (2010 was the most productive, with 11) — and more than three months remain in the 2015 season.

This trend partly reflects the fact that BA’s top prospects in 2015 were particularly green. Only three of this year’s top 20 had previously debuted (such players can be ranked if they still have rookie eligibility), resulting in more players who could get called up for the first time. In contrast, four of the top five prospects in BA’s 1990 rankings had already reached the major leagues.

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MLB draft pick success rate


About two-thirds of first-round draft picks have reached the majors in recent decades, but the success rate drops off steeply from there, falling below one-third by the fifth round and one-fifth by the 10th. MLB recently shortened the draft from 50 to 40 rounds, eliminating a few 4-percent longshots from the back end of the draft (most likely converting them to undrafted free agents). Note that this data includes all players drafted, regardless of whether or not they signed that same year.

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The value of top prospects

How valuable is a top prospect?


The above chart shows each of Baseball America’s Top 100 prospects who were listed as position players, as well as their Wins Above Replacement ( version) in their first seven seasons, roughly corresponding to the period of team control before free agency. The most striking feature of the chart is the variance — top prospects tend to be more valuable, and the collection of “busts” around 0 WAR increases as the ranking gets worse, but the outcomes vary considerably throughout the spectrum.

The best-fit line shows a logarighmic relationship between ranking and expected WAR (i.e., WAR varies with ln(rank)). A top-ranked position-player prospect is expected to be worth almost 20 WAR in his first seven seasons, while a #100-ranked hitter is expected to be worth less than 5 WAR.

Albert Pujols (ranked #42 in 2001) is the lonely outlier at the top of the chart. Jeff Bagwell (#32 in 1991), Chase Utley (#81 in 2003) and Ichiro (#9 in 2001) are the others above 40 WAR.


The upside is a bit lower for pitchers, but the variance remains — the ranking-WAR relationship is even weaker than it was for hitters (R-squared = .05 for pitchers, .10 for hitters). A #1-ranked pitcher is expected to be worth about 12 WAR in his first seven seasons, while a #100-ranked pitcher is expected to be worth 3 WAR. (Only three pitchers have been ranked #1 since 1993, most recently Daisuke Matsuzaka in 2007.)

Roy Oswalt (#13 in 2001) is currently the most valuable pitcher on this graph, though Clayton Kershaw (not pictured, but #24 in 2007 and #7 in 2008) should edge him by the end of this season, his seventh.


Combining the two groups, we see that top-100 hitters tend to be worth more than top-100 pitchers, most notably at the very top of the rankings. A #1-ranked pitcher projects to be worth about as much as a #10-ranked hitter — but the expected value of hitters drops more quickly than the value of pitchers, suggesting that hitters may be easier to rank than pitchers.

WAR in seasons 1-7 collected via the Play Index. Follow: @DiamondGraphs