Prospects are all the rage in the world of fantasy baseball nowadays. Whether it be due to the popularity of keeper and dynasty leagues taking off, or the fact that every discussion about trades between major league teams involves trying to figure out what prospects will switch organizations potentially, prospect talk is everywhere. That raises an interesting question though, how do you know just how good a prospect is based on numbers they’ve put up in the minor leagues? It should seem like a straightforward question right? A guy has a great year at Double-A or Triple-A and clearly he’s ready for the majors and to be a key piece to an offense, however it’s just not that simple. With as many different leagues and levels as there are in the minor leagues, some numbers and stat lines aren’t equivalent to others, but don’t fret there are some key stats to look at that can help you utilize those minor league stats to make the right call on which young players to go after in drafts or the waiver wire.

While it’s true that many fantasy baseball leagues don’t count sabermetric stats in the counting categories or the ratios, they can’t be fully ignored because often they are quite a good way to explain why a guy had a year he had or didn’t have a year he was expected to in the majors. The same can be said for evaluating minor leaguers as they get ready to be called up to the bigs.

Last year the baseball world was taken by storm by Fernando Tatis Jr. but was that breakout out of the blue or could we see it coming? In 2016 he played 55 games in rookie ball and Low-A with a .273 average, .311 OBP, four homers, and 15 RBI with a .348 BABIP and .341 wOBA. In 2017 he split time between A-Ball and Double-A with 131 games played with a .278 combined AVG, .379 OBP, and .343 BABIP, and .390 wOBA with 22 homers and 32 steals. The 2018 year saw him spend the whole time in Double-A with 16 homers, 16 steals, and a .286 AVG and .370 BABIP in 88 games. Are we seeing a theme here? He got better at every step, he didn’t just tread water, he improved the higher he climbed, and the advanced metrics show that too including wRC+ which started just over 100 and climbed to 150 last year in the majors. So we want to look for trends in the numbers going up and not just staying the same.

A guy like J.P. Crawford who was also a top prospect for a few years is essentially the opposite of Tatis as Crawford got worse the higher he climbed. In 2014 across A-ball and High-A he hit for a .285 AVG and a .317 BABIP, in 2015 across High-A and Double-A he hit for a .288 AVG and .315 BABIP, in 2016 across Double-A and Triple-A those fell to a .250 AVG and .287 BABIP, and 127 games at Triple-A in 2017 those fell again to .243 average and .275 BABIP. In his 165 games in the majors split between the Phillies and Mariners, he’s hitting .222 with a .281 BABIP and relatively light on counting stats. That trend should’ve suggested to potential owners that the MLB stat lines were coming for Crawford who was always a glove-first type prospect.

Hitter Call-up Conundrum

Every season there are hitters that are called up in the middle of the year and getting them on the waiver wire can be the key to your league victory, but just because they are having a great year in the minors, can you tell which ones will be valuable in the majors and which ones will struggle? Let’s take a look at a few of the bigger names that came up last year and see why the succeeded or failed in their call-ups.

Yordan Alvarez won the AL Rookie of the year award after his spectacular 87-game run with the Astros last year that resulted in a .313/.412/.655 slash line and 27 homers. The question is, was that out of the ordinary for him? In 2017 split between A-Ball and High-A he slashed .305/.378/.481 in 90 games with 12 homers, 69 RBI, 45 runs, and eight steals, the 2018 campaign saw him split between Double-A and Triple-A and he put up very similar counting stats and the batting average stayed at .292 and the BABIP went from .360 to .346, so pretty close. In 2019, he really started to get noticed and while the complete counting stats line jumped up, he did play 142 games between Triple-A in the Pacific Coast League and the majors which both used the juiced ball. The 2018 counting stats extrapolated for 162 games shows 37 homers, 136 RBI, 116 runs, and 11 steals compared to the 2019 line of 50 homers, 108 runs, 149 RBI, and two steals. So the answer is it was not out of the ordinary because again, he followed the trend of improving with each level he jumped to.

Keston Hiura was another big name call-up in the middle of last season, and just like Alvarez he had a trend of getting better the higher he rose in the Brewers’ system. The averages and BABIPs all improved and the counting stats all get better as well. The other thing is that his walk rate improved each year as well, meaning he wasn’t being fooled by the increased breaking pitches and off-speed offerings he was seeing as the level got higher which is also an important thing to look at too. So like Alvarez, the trend was there for him to be as good as he was in the majors.

Now if we talk about Isan Díaz, another second baseman who was a bit of a highly targeted add when he first came up, the opposite trends are true. Diaz spent all of 2016 in A-Ball for the Brewers and hit .264 with a 25.2-percent K-rate in 135 games and hit 20 homers. In 2017, it was all A-Advanced for 110 games while he hit .222 with a 26.6-percent K-rate and 13 homers. Then 2018 came, his first in the Miami system, and he combined for 119 games split between Double-A and Triple-A, hitting .232 with a 27.4-percent K-rate and 13 home runs and the BB-rate dropped to 13.3-percent. While the numbers for Diaz in Triple-A in 2019 were very good (.305 AVG and 26 home runs in 102 games) it was with the juiced ball and his MLB numbers in 49 games followed the trend of decreasing ratios for him. In 49 games, he hit just .173 with a 29.4-percent K-rate and five home runs in 179 at-bats. If you had spotted the trends in his lines, you’d have likely avoided the downturn he produced for those who rostered him.

Pitcher Call-Up Conundrum

Each year more pitchers are called up to the majors for their respective teams than hitters, so it’s perhaps more important to know how to use minor league pitcher’s numbers in your research. Pitchers have a decided advantage in at-bats since they are the ones controlling what’s coming next and how they will exploit a hitter’s weaknesses, akin to a quarterback having an advantage over a defense since they know what play was called and where to hit the openings in the coverage. That can make looking at raw numbers easier to do, however there are still things to keep in mind.

One of the most telling stats of a pitcher’s success is not the K/9 rate, though that is all the rage right now as fantasy owners and reality GMs try and stack their roster with the most strikeout-providing arms possible, it’s K/BB ratio. While it is critical to rack up the strikeouts for both your season totals and keeping guys off base or from making contact, it’s equally as important to not issue free passes. The pitcher’s that excel in high K/BB are the elite arms in the game and the best prospects coming up. Last year’s darling, Chris Paddack , pitched 177.2 innings in the minors before breaking camp with the Padres last year and in that time he posted 230 strikeouts to just 20 walks. Nope that’s not a typo…an 11.5 K/BB ratio. So it shouldn’t have come as a shock to fantasy players to see him post the near five-to-one K-BB ratio in the majors over his 140.2 innings.

So much of what the pitcher’s numbers turn out to show is a reflection of the defense behind them and a lot of luck for where the batter hits the pitches. However, there are stats that mostly eliminate the defense and luck aspects that are a good determinant of future success as a major leaguer. Ground Ball percentage is one of those stats. If a pitcher keeps the ball down a lot, it’s harder for opposing hitters to get hits or string together hits to create scoring chances, and it’s easier for the pitcher’s defense to get double plays and get out of innings sooner. If we take a look at another stud rookie from last year, Mike Soroka , he pitched 370.2 innings in the minors before pitching his first full season in Atlanta last year and in those innings he posted a 51.1-percent GB-rate, nearly equaling his 51.2 mark in Atlanta over 174.2 innings. When looking at a second stat, HR/9 or the measure of how well a pitcher keeps the ball in the park, you see he had a 0.3 mark HR/9 in that span in the minors, and it’s starting to be easy to see why the stat line was what it was for the Braves in 2019.

The last stats to focus on when looking at how a pitcher’s minor league numbers will translate is to look at their FIP and xFIP. Both stats, Fielding Independent Pitching (FIP) and Expected Fielding Independent Pitching (xFIP), are better measures of what a pitcher is actually pitching like rather than ERA assuming league-average fielding and BABIP rates for FIP and then adding league-average home run rates for xFIP.  If we stick with Soroka and Paddack, looking at their FIP and xFIP marks in their minor league careers, you see Soroka with 2.81 and 3.12 marks respectively, which are just a touch lower and a touch higher than his 2.84 career ERA. In the case of Paddack, over his 177.2 innings he posted a 1.82 ERA, 1.93 FIP, and 2.09 xFIP which are all very close to each other. Having those marks all be close indicates in both Soroka’s and Paddack’s cases that they were pitching as good as the ERA indicated they were and thus their successes in the majors wasn’t a surprise.

Trust Your Research

In all likelihood, you’ve been watching these guys for a bit and aren’t just stumbling upon them because you saw the latest news report on an impending call-up. If you have in fact been following them for a little while or more than a year, you’ll know what they’ve done at what levels and how they look against better competition. Trust your knowledge, your research, and your gut. The best tool you have is your own gut feelings about things and the time you put in to knowing who is worth taking a shot on and who’s not. So, all told do your research with the above kind of stats in mind and you should be able to get your hands on the guys more likely to succeed than not.