There’s no more fun certainty on #BaseballTwitter than the certainty that exists about which prospects are going to be awesome. We’re all guilty of it at some point, myself included. It gets even worse when a fanbase brands a group of players together, like Generation K or the Killer B’s, so when one departs or fails, there’s an overwhelming sense of “hey you’re breaking up the band.” It starts earlier and earlier, with Boston’s “Big Four” the latest example. And with Anderson Espinoza heading across the country to meet up with the rest of his former Red Sox farmhands, there is now just a “Big Three.”

But rather than view Espinoza as the member of this future foursome who would transform the organization, let’s view him as part of a similarly arbitrary group to try to get a sense of the historical significance of what the Padres are getting and the Fightin’ Dombrowskis are losing. The right-handed fireballer was the fifth-best pitching prospect in baseball as of last week, when we released the mid-season top 50. And while some slight eligibility discrepancies exist between the mid-season list and The 101, they are mostly muted because the pitchers who have pitched fewer than 50 innings, but were in the majors at the time of publish, are both likely to lose their eligibility prior to the season’s end. So who have the fifth-best starting pitching prospects been in the 10 years we, at Baseball Prospectus, have been setting Top 101s ablaze into the ether? And how have they performed before hitting free agency? No, put your phone away.

2016: Tyler Glasnow (0.1 WARP; 4.05 DRA; all but one start left)
There’s almost nothing we can draw from Glasnow’s last six months that will leave us more or less confident about what he’ll be through the duration of his service time. So let’s just move on.

2015: Jonathan Gray (2.5 WARP; 3.64 DRA; 5.5 yrs left)
The Rockies have gotten a bad reputation for developing starting pitching, and it’s been well deserved. However, Gray may yet prove to be the exception to that rule. He won’t be a free agent until after the 2021 season, so there’s plenty of time left for things to go very right or very wrong.

2014: Yordano Ventura (2.9 WARP; 4.50 DRA; 3.5 yrs left)
The diminutive right-hander may be the best physical comp for Espinoza among these 10 pitchers, but the circumstances around them being elevated on prospect lists was very different. Ventura was 22 years old and had already surfaced in the majors in 2013, flashing devastating fastball velocity and stuff. Since then, he’s been hounded by inconsistency and a propensity for drilling opposing hitters—not a combination known to endear oneself to the greater public. He’s also been a below-average starter who can’t even claim to be much of an innings eater.

2013: Taijuan Walker (4.6 WARP; 3.86 DRA; 4.5 yrs left)
It hasn’t always been pretty from a raw stat perspective, but Walker has a reasonable chance to finish as the best of this bunch. He misses bats at nearly one per inning and, aside from a shoulder impingement that kicked off his 2014 season, he’s been reasonably healthy throughout his professional career. He was billed as the second-in-command to the King in Seattle, and when said King is healthy, that appears to be exactly what is developing.

2012: Shelby Miller (5.6 WARP; 4.28 DRA; 2.5 yrs left)
It’s almost incredible that Miller doesn’t have both more and fewer wins than he does, given how all over the map his career has been. He’s been a savior, he’s been hurt, he’s been broken, he’s been strangely missing in the playoffs, he’s been great, he’s been the centerpiece of one of the worst trades of the decade, and now he’s been demoted to Triple-A. Those 2013 and 2015 seasons were great, and Miller earned 120 percent of his WARP between those two campaigns. The simple fact that the math works out that way just goes to show how bad he’s been over the remainder of his career. But don’t worry, Diamondbacks fans, one or two of those top shortstop prospects in the minors today has to bust (the numbers tell us so), and maybe it will be Dansby Swanson.

2011: Matt Moore (7.0 WARP; 3.99 DRA; 1.5 yrs left)
The year before the can’t-miss lefty was the no. 1 prospect in all of baseball, he was simply a great prospect who was coming off a minor-league-leading 208 strikeouts (in just 144 2/3 innings!), which happened to be his second year in a row lapping the field in the category. He burst onto the scene in late 2011, culminating in another strong season with a dominant start against the Rangers in the playoffs—throwing seven shutout innings to take Game 1 on the road. Unfortunately for Moore, the bats that swung through and over his pitches in the minors were less patient than the ones who watched them miss the zone in the majors, leading to exaggerated walk totals and high pitch counts. Diminished velocity and Tommy John surgery later followed. Even now with the velo trending back up, he’s swapped his walk issues with longball issues, and is having a tough time making his extremely team-friendly (at the time) extension as team-friendly as it should be.

2010: Martin Perez (1.2 WARP; 4.84 DRA; 2.5 yrs left)
Having long been a Perez apologist, it truly saddens me to see him as the least valuable of this entire group throughout his career thus far. And this actually might be the best true comp to Espinoza of the bunch. When Kevin Goldstein ranked Perez as the 15th overall prospect in 2010, he had spent most of the year in the Sally League before making five starts in Double-A as an 18-year-old in the season’s twilight. Perez was (and Espinoza is) a young 6-foot-nothing with extremely good stuff and advanced command and control for his age. Sure, Perez didn’t touch 100, but a left-handed pitching prospect that touched 96 was just as much of a unicorn seven years ago.

The road was anything but smooth for Perez from then on. He struggled in the upper minors for a few season and was essentially left for post-prospect purgatory by the age of 22. And by the time he finally was able to have some major-league success, his elbow had finally given out and he spent much of 2014 and 2015 recovering from Tommy John surgery. Finally two years removed from going under the knife, he’s back to the strong velocity of his early prospect years, but has still really struggled to miss bats and looks to be a back-end starter at this point.

2009: Tommy Hanson (9.0 WARP; 4.19 DRA)
Besides being a tragic story, Hanson was a tremendous prospect, blowing through the Braves farm system toward the end of last decade. His was shaping up to be the career of a very good mid-rotation starter, but a bout of shoulder issues in late 2011 spelled the end of the road for him, as his velocity dropped by nearly 3 mph between the end of 2010 and the start of 2012. Pitching prospects don’t often meet such a dramatic professional end, but Hanson is a tough reminder that even pitchers with big, strong builds can see those bodies fail them at any point.

2008: Homer Bailey (8.0 WARP; 4.51 DRA)
One of the most highly regarded pitching prospects of the decade; Bailey was actually already trending down by this point, as he was ranked higher as a prospect the year before when he was coming off his dominant stretch in Double-A. It took a long time for his command and control to get to the point where he could sustain any sort of success, and as that happened, his velocity dipped and his stuff lost its crispness. In 2013, he finally regained that lost arm speed and spent the next two years as a very good mid-rotation starter before it all became too much for his UCL. The Reds signed him to a six-year deal worth around $100 million prior to hitting free agency (while he was at the top of his game), and every day they regret it. He still has not pitched in 2016.

2007: Yovani Gallardo (17.2 WARP; 4.20 DRA)
He may be a shell of his former self now, but Gallardo represents a very good outcome for a pitching prospect of this ilk. The former top Brewers prospect is the only pitcher on this list to register two separate four-win seasons, back in 2009 and 2010—and these came after he tore his ACL in 2008, missing nearly five months. This is the pattern of pitchers that we’re used to. First-year struggles followed by success through development and a peak that’s cut too short by normal wear and tear leading to velocity loss. This is textbook success for a pitching prospect.

That’s a lot of names. Names you know. Names you’ve seen succeed, but no one who’s turned into a star-level pitcher. On the flip side, there’s really been no complete bust either—unless you’re writing off Perez already. In total, it all adds up to 58.1 WARP in approximately 38.5 seasons—or just over 1.5 WARP/year of service time. Maybe Anderson Espinoza will be the exception here and turn into a star, but maybe this is, as Barney Stinson might have put it, the Cheerleader Effect in baseball terms. Either way, whoever wins or loses yesterday’s trade is likely to have much more to do with how real and good Drew Pomeranz is right now than which tail of the bell curve Espinoza ends up at.

Thank you for reading

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Does age play into this at all? I honestly don't know the age of all those dudes when they were the fifth best prospect, but doesn't being the fifth best so young affect things, in terms of projected ceilings and floors?

Not a comment on the trade. Okay, I should just look it up.
Glasnow: 22
Gray: 23
Ventura: 23
Walker: 20
Miller: 21
Moore: 22
Perez: 19
Hanson: 23 :-(
Bailey: 22
Gallardo: 21
Espinoza: 18
You would expect that the younger a player is when he ranks in a certain position on a prospect list, the greater the upside/risk is. That said, there's some self selection here, as even close-to-the-majors prospects don't rank that highly unless they have significant upside and the far-away prospects tend not to rank that high unless they have a comparatively high floor for someone of their age. This probably mutes the effect a bit.