Perhaps the most asked question during the fantasy baseball season, and just before it starts, is regarding call-ups and potential call-ups. Clearly getting the new, hot, young thing on your roster is a big part of bolstering your team’s stats during the season but missing on a guy like that can be see you drop down the standings quickly too. The world of minor league baseball can be complex to parse given the many different leagues and levels and stiffness of competition a prospect can be exposed to. However, there are a few hallmark stats to look at that can be helpful predictors for how a prospect may fair when reaching the majors.

While it’s true that many fantasy baseball leagues don’t in fact 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 good 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.

One look at Ronald Acuna Jr.’s rookie year and you will see a guy that helped in five categories to whomever was the look owner that picked him up either in the draft or on the wire in a FAAB bidding war. In 111 games, Acuna hit for a .293/.366/.552 slash with 26 homers, 78 runs, 64 RBI, and 16 steals in his rookie campaign, ultimately garnering the NL Rookie of the Year award. Looking back at his minor league numbers you will see that he improved in not only his traditional stats at each level but his sabermetric ones improved too from BABIP to ISO to K% to BB% to his wOBA. These are the kind of guys that you want to look for when surmising who will translate well to the major leagues and who won’t.

A guy like J.P. Crawford who was also a top prospect for a few years is essentially the antithesis of Acuna 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. Now over 72 games at the major league level, all with Philadelphia, he hit .214 with a .294 BABIP in a good hitter’s park. Had you been watching his stats, you’d have known he wasn’t going to succeed from the plate at the big leagues and was simply moving up based on defensive ability.

Hitter Call-up Conundrum

There are certain guys who were called up because they possess copious amounts of one particular skill the team needs. Players like Joey Gallo , Billy Hamilton , and Khris Davis are prime examples of one-skill guys. Gallo has power for days, Hamilton with speed, and Davis with power as well. It is sometimes necessary to use one guy to fill a specific stat category on your roster, sure, but the trick is deciphering whether that skill will play at the major league level or if they were just taking advantage of subpar minor league competition.

A key tool in deciphering potential success is looking at the K:BB ratios and the K and BB percentages at each level. Khris Davis is a great example of this. Every year he played near a full season in the minors, his K-rate was just over 20-percent, which isn’t great, but his BB percentage was around 13-percent, which is elite, and combine those with his steady ISO marks of near .230 and you get the picture that what he’s doing in the majors isn’t a shock. The reverse of that is Billy Hamilton . Hamilton is a speed demon but in order to use it needs to be on base, so you’d expect him to put up high BB rates and low-K rates right? Not quite though good guess. He consistently had single-digit walk rates in the minors and consistently had near 20-percent K-rates as well. Couple that with his near 50-percent GB rate (the rate at which the hitter hits a ball on the ground) and you have a recipe for exactly what we’ve seen from Hamilton in the pros.

ISO is a stat that comes in incredibly handy when looking at the ability to translate power numbers to the majors as in the case of Joey Gallo and Khris Davis . For those that don’t know what ISO refers to, it’s simply subtracting the batting average of a player from their slugging percentage to get a pure power mark. Gallo had ISO marks over .250, elite, at Double-A and then repeated that at Triple-A and has improved on it in the majors meaning the power he’s shown is sustainable. Davis posted slightly lower ISO marks but still in the upper echelon and hence his three-straight years of 40-plus homer pop.

Pitcher Call-Up Conundrum

Each year more pitchers are called up to the majors for their respective teams than hitters are 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 QB 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, Walker Buehler , spent his pro career putting up stop after stop of 3.00 or better K/BB ratios with just 12 total innings in which it registered below that mark. Look at what happened when he came up in earnest last year, he was outstanding all the way through the World Series because he didn’t give up free passes and elongate 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. A lot has been made of Sonny Gray ’s move to Cincinnati this offseason but his career 53.4-percent GB rate indicates he will be good at keeping the ball down in the home run haven that is that ballpark. If we harken back to Buehler, in the minors his lowest GB rate was a 51.3-percent and he had numerous stops over 60-percent. Coupled with the ground ball rate, HR/9 is another good tool to use to see how hard the pitcher is being hit. Justus Sheffield is a guy that has flown a bit under the radar this offseason despite the fact that he’ll be in the starting rotation for the Mariners likely from the get go. In his minor league career to this point, with two different organizations prior to joining the Mariners, his GB% has been in the mid-40s the whole time, which is a bit lower than we’d like to see, but his HR/9 has only topped .57 once in nine minor league stops. Giving up about a half a homer per nine shows he’s great at keeping the ball in the park which will help in the big confines of Seattle’s home park.

The last stat to focus on when looking at how a pitcher’s minor league numbers will translate is to look at their FIP. Fielding Independent Pitching, FIP, takes defense and bad luck out of the equation for a pitcher and shows what they actually pitched to ERA-wise if they’d have had standard defense behind them. In Walker Buehler ’s case, his FIP was almost always lower than his ERA meaning that he was hurt by substandard fielding and defense, whereas Justus Sheffield almost always had a FIP higher than his ERA showing that he wasn’t actually pitching as well as his ERA credits him with and was being helped by better than standard defense. You want to find guys whose FIP is either right around their ERA or below it since they are the more likely ones to do well in the majors.

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 and 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.