Due to the success of those players, owners might be more willing to take a shot on a top prospect this year. But, as we know, the failure rate of prospects is high, and even the great ones need a year or two of seasoning in the majors before reaching their potential. That complicates things for fantasy owners, as players who offer such a high reward are the most unpredictable assets in fantasy drafts.
Just how difficult is it to hit on a rookie phenom? Using Baseball America’s annual prospect rankings, which go back to 1990, I looked how players on those lists performed in the season in which they lost their rookie eligibility. This excludes players like Wade Miley , because, let’s face it, if you’re using a draft pick on a rookie, it’s going to be a guy who was touted on a top prospect list. Looking at the year the player lost their rookie eligibility was important because, if you’re drafting a prospect, you’re doing it with the expectation that he’s going to receive a significant amount of playing time. I also excluded the two strike seasons, 1994 and 1995, as the shortened season would have given us wonky values for guys who played during those years.
In order to figure out a player’s value, I enlisted the help of Zach Sanders. Zach has a formula he uses to produce the end of season fantasy rankings on RotoGraphs, which he explains in further detail here  and here.  The formula takes the typical 5X5 fantasy stats, factors in playing time, and puts out a dollar value for each player. Typically, any player with a value above $0 turns out to be useful in most fantasy leagues. Obviously, there’s a big difference between guys who were worth $3 and guys who were worth $23, so I broke it down into tiers.
|$29-$20||Top player at their position|
|$19-$10||Starter at their position|
|$9-$5||Part season starter/injury fill in|
All but the final tier are pretty self-explanatory. The 25th man is the type of player who teams might hold onto for an entire season, but is always close to being cut. A good example of a 25th man from last season is Jesus Montero . Teams that invested a draft pick may have held onto him in case he put together a good stretch, but he was probably rarely used by his owner. The cut off technically doesn’t end at $0, as guys who were just below that threshold can pretty much be lumped together, but you get the idea.
Drafting prospect hitters often ended in disappointment. Of the 306 hitters in this study, only 89 produced positive value. That’s good for a 29% success rate. The average value produced by a prospect hitter since 1990 was -$4.36. Far under fantasy replacement level.
Things improved with pitchers. There were 140 pitchers used in the study, including starters and relievers. (Technically, there were 139, but Anthony Young  saw time enough time as both a starter and a reliever, so I counted him at both positions). Of those 140, 59 of them produced positive value during their rookie year, good for a 42% success rate. The average value produced by pitchers turned out to be -$0.84. Perhaps surprisingly, pitchers were far more likely than hitters to produce positive value during their rookie seasons.
This may seem incredibly obvious, but playing time is a huge factor in determining whether a prospect will have value over the course of an entire season. That can be challenging, too, as managers rarely show their hand with rookies before the beginning of the season. Hitters who were able to produce a positive value over the course of an entire season, on average, had 506 at-bats that year. The players that produced negative value averaged only 279 at-bats. Drafting a prospect only makes sense if you know for sure that player is going to be in a full-time role, or will be up within the first two months. Guys that come up around mid-season can produce value, but the chance of that happening is extremely slim.
The same thing applies for pitchers. The pitchers that managed to produce a positive value averaged 131 innings per year, while the guys that produced a negative value received only 88 innings per season. Those numbers don’t necessarily apply for relievers, who can be effective in fewer innings depending on their role. Though of all closers who produced a positive value, Jonathan Papelbon  had the lowest inning total, at 68.1. So, relievers still need to see significant innings in order to produce value.
Let’s assume that you are guaranteed to find a prospect who is going to produce a positive value. You’ve done your homework, and you know which players will receive playing time, and that those players will produce. We can attempt to figure out how well a successful prospect performs on average. We’re going to call this “best-case value,” since it represents the likely value you’ll receive if you draft a prospect most likely for success.
The best-case value assigned to all successful hitting prospects is $9.65. In an ideal situation, you’re likely to wind up with a borderline full season starter, or a really strong bench player. Playing time once again is a major factor here, as hitters who receive at least 500 at-bats were slightly better, with a value of $10.17. For reference, here’s a full breakdown of how prospect hitters performed during their first year in the majors.
|Year 1 Hitters (n=306)|
*The (#) indicates how many players were in the sample.
The best-case value from starting pitchers is slightly lower, settling at a value of $8.50. With pitchers, however, getting a guy who is going to throw a ton of innings doesn’t always work to your advantage. Among those pitchers who tossed at least 100 innings, the average value produced was just $3.38. This seems to indicate that, while innings are important to determining value, plenty of rookie pitchers have poor seasons, but still throw a lot of innings. Even in a best case scenario, it’s tough to end up with a pitcher that falls into the “starter at their position” category. You’re more likely to get a part-season starter if you opt for a rookie pitcher.
|Year 1 Pitchers (140)|
If you’re drafting a rookie pitcher, you’re better off going with a reliever, but only if you believe that reliever will jump into the closer role. Players with at least 10 saves ended up producing a best-case value of $9.98. Only one of those players, Addison Reed , had a negative value on the season, and Reed was close enough to the $0 threshold to still be useful. Basically, don’t draft a rookie reliever unless you know he has the job.
Drafting a prospect
Now that we know the average value of all prospects, and the average value of prospects in a “best-case” scenario, we need to determine whether it’s worth it to draft prospects at all. And, if so, we need to determine what round you can justify spending a draft pick on one of these players. Again, we’re going to work with our “best-case” values, because if you’re drafting a prospect, you’re expecting them to receive a ton of playing time, or, in a reliever’s case, a closer role.
|Position||Average Value||End of season rank|
The chart above shows the average value at each best-case position, and where those players would rank in a standard 12-team fantasy league. That means, in an ideal situation, you earliest you should draft a prospect is in the 10th round. And with that pick, you should take a closer. For prospect hitters, you should wait until the 11th round, and for starting pitchers, you should wait until round 12. If you are absolutely certain that a hitting prospect will receive at least 500 at-bats, you might be able to justify taking that player about the same time you would take a rookie closer. Remember, these are the best-case scenarios, so this is the absolute earliest you could pick a “sure thing” before it’s considered a major overdraft. This is the most optimistic scenario.
This value system obviously doesn’t work in keeper leagues, where owners are looking at a player’s long-term value. However, it can help us determine whether there is hope for prospects that fail during their first season. Since Sanders’ value system places a large value on at-bats, most of the really bad performances were guys that only received a low number of at-bats, or late-season call-ups. Even if they performed well, they didn’t receive enough opportunities to be useful in fantasy leagues. In order to try and find legitimately bad rookie performances, I looked at all players who had received at least 400 at-bats. That’s a good cutoff, as it shows guys who were given chances at significant playing time during their first season, and did not produce.
For hitters, having a poor rookie season isn’t necessarily a harbinger of doom.
|Prospect Hitters (#)||Positive value||$30+||$29-$20||$19-$10||$9-$5||$4-$0|
|Year 2 (30)||33%||0%||0%||10%||6%||16%|
|Year 3 (29)||58%||0%||6%||20%||13%||17%|
|Year 4 (27)||41%||0%||4%||11%||18%||7%|
*The (#) indicates how many players were in the sample. The sample number drops as recent players haven’t progressed far enough in their careers to be included, and we had to eliminate guys who played during the strike.
Of the 30 hitters who produced negative value during their rookie season, a third of them rebounded and entered fantasy relevance in their second year. Things got even better for hitters during their third season, when 58% of that same group produced a positive value. During their fourth major league season, that number only dropped slightly, settling at 41%.
You’ll also notice that players still don’t always live up to their prospect status in their second season, as no player produced within the $29-$20 range. However, you do start to see a better payoff from these players during their third year in the league. As the 58% success rate indicates, the third year seems to be the time when most prospects that struggle initially start to establish themselves. Looking ahead four seasons is helpful, but not perfect, as you still see some players’ values fluctuate. Guys like Alex Gordon  and Pat Burrell  produced negative value during the fourth seasons in the majors, but still managed to carve out useful fantasy seasons afterward. But if a guy struggles to produce in each of his first three seasons, there’s virtually no hope he’ll turn into a useful player.
We get somewhat similar numbers with starting pitchers.
|Prospect Pitchers (#)||Positive value||$30+||$29-$20||$19-$10||$9-$5||$4-$0|
|Year 2 (26)||46%||0%||7%||19%||7%||11%|
|Year 3 (23)||39%||0%||8%||13%||13%||4%|
|Year 4 (18)||44%||5%||5%||16%||11%||5%|
Pitchers that struggle in their first seasons have a much better success rate in year-two. That success rate seems to carry over to others seasons, as we see a more consistent success rate from pitchers. There’s no third season surge here, potentially telling us it might be easier to judge pitchers after just two years of production. The guys that fail to establish themselves either are pushed out due to ineffectiveness or injury, causing the sample to drop to just 18 players in year-four. Another reason the sample is low during that fourth year is because many pitchers in this study are current players who haven’t been in the league long enough. This is somewhat of a make-or-break season for guys like Zach Britton , Jake Arrieta  and Mike Leake . If they don’t show signs of effectiveness this year, they could fall out of favor with their current teams.
Running this study with relief pitchers doesn’t work as well, since their fantasy value is often based on their role. However, it’s a good bet that if a pitcher struggled and didn’t receive save opportunities during their rookie season, they were unlikely to move into the closer role the following year. Teams often give that role to players coming off strong performances.
Guys like Mike Trout  and Bryce Harper  are the exception, not the rule. If you’re going to spend a draft pick on a prospect in a re-draft league, you’re likely to be disappointed. Even if you hit on the right player, the reward generally doesn’t produce a full-season starter. Very few prospects turn into useful fantasy assets their first season in the majors, and only by waiting until late in your draft and being sure that your rookie will get plenty of playing time can you mitigate your risk somewhat. A decent chunk of struggling rookies figure things eventually, too, making them a much better bet in keeper leagues.
Concerns about playing time and production makes drafting prospects arguably the riskiest strategy a team can employ. The reward is rarely ever worth the risk.
*For a look at the complete list of hitters and pitchers, I created a Google Doc, which can be seen here.