A Brief Report on Junior Guerra, the 30-Year-Old Prospect

Even for those readers who regard Gary Huckabay’s contention from the late 90s that there’s no such thing as a pitching prospect — even for those who regard it as perhaps an exercise in hyperbole, the notion of a 30-year-old pitching prospect likely sounds absurd. Prospectdom, first of all, implies some degree of future potential, which itself implies some degree of youth. And second of all, what information exists regarding aging curves suggests that, if a pitcher wasn’t a prospect at 20 or 25, there’s little reason to suppose that he would be at 30, with years of abuse behind him already.

And yet, in the absence of that word (i.e. prospect), there’s a shortage of appropriate terms for what White Sox right-hander Junior Guerra is. At 30 years and 118 days, he’s made zero major-league appearances. Indeed, he recorded his first Triple-A appearance* just last Thursday. His rookie eligibility, in other words, is not in question. And yet, as noted in yesterday’s edition of the Fringe Five, Guerra has produced one of the top strikeout rates among all qualified minor leaguers while also exhibiting sufficient arm speed to suggest that his success isn’t the product merely of deception or veteran wiles.

*Affiliated Triple-A appearance, that is. Guerra played for Yucatan of the Mexican League in 2012, where he produced an unambiguously poor 20:22 strikeout-to-walk ratio in 28.0 innings.

Guerra made his second Triple-A appearance ever shortly after that newest installment of the Fringe Five was published. The purpose of this post is to report the absolutely most basic information regarding that start — and, probably mostly, to provide more footage of Guerra’s repertoire.

With regard to results, Guerra acquitted himself well, producing an 8:3 strikeout-to-walk ratio against 25 batters over 6.0 innings (box), leaving him still with one of the top-10 strikeout rates in the minors.

With regard to velocity, he sat at 91-94 mph throughout the game, as exhibited by the following GIF, which depicts Guerra throwing a 94 mph fastball in his sixth and final inning:

JG FA 94 in 6th RL Foul

Perhaps unsurprisingly, Guerra was most effective against right-handers, recording six of his eight strikeouts against Louisville’s Ryan LaMarre and Yorman Rodriguez. His slider, which sat at about 86 mph, was responsible for many of those swings and misses. Here’s an example of that same pitch — in this case LaMarre:


And the same thing in slow motion:


Guerra’s most impressive pitch, when at its best, is his changeup (or splitter or split-change). Here’s an example of same to Irving Falu, which batter has produced a minor-leauge strikeout rate below 10% (and major-league strikeout rate of just 10.8%, actually, in 130 plate appearances):


And in slow motion, as well:


We hoped you liked reading A Brief Report on Junior Guerra, the 30-Year-Old Prospect by Carson Cistulli!

Please support FanGraphs by becoming a member. We publish thousands of articles a year, host multiple podcasts, and have an ever growing database of baseball stats.

FanGraphs does not have a paywall. With your membership, we can continue to offer the content you've come to rely on and add to our unique baseball coverage.

Support FanGraphs

Carson Cistulli has published a book of aphorisms called Spirited Ejaculations of a New Enthusiast.

newest oldest most voted

His BRef page has all his indy ball and winter league glory


He’s almost never been outright good in any league or level that he’s had significant time in.


I’d love to know what he did in the Italian League in 2014 – apparently that hasn’t been loaded into BRef just yet.

It looks like he was a failed catcher in the Braves system who got converted to pitching at age 21, didn’t stick, got a brief look from the Mets at age 23 and didn’t stick, and has been bouncing around since then.


He was pretty good in the Venezuelan Winter League. He even showed up on Carson’s SCOUT leaderboard:


I can’t find his numbers playing for San Marino, but I know he was 8-1 with an ERA of 1.29, so he was probably pretty good there too. If anyone wants to try to find his numbers and can speak Italian (Google translate did not help me), you can try San Marino’s website:



Yeah, he’s been good there the last two years or so. But his career numbers there probably aren’t very good.