Miguel Sano’s raw power blew me away the first time I watched him swing. His rookie season was one of many bright debuts, but no other rookie matched his power by the eye test. He hit home runs with the calm assuredness of Edwin Encarnacion, the authoritative stroke of Mark Trumbo, the explosive force of Nelson Cruz.

If you’re a person who likes the concept of eye tests, but doesn’t trust them (a skeptic), then ISO is the statistic you go to for quantification. It measures power by weighing extra base hits relative to each other. It’s really not a complicated formula, so I think it’s worth including here.

ISO = (Doubles + 2*Triples + 3*Home Runs)/At Bats

It’s better than slugging percentage for isolating a hitter’s true power because it cannot be artificially inflated by a lot of singles.

I went to FanGraphs and searched for the highest ISO marks posted in rookie seasons since 1969, setting a plate appearance cutoff at 350. Sano showed up at #18 with a .262 ISO, but at No. 6 was another 2015 rookie that caught me off guard: Randal Grichuk. With a .272 ISO.

I’m sure those of you who watched every Cardinals game last season religiously won’t be too surprised by that historic ISO, but for the rest of us, this is news. To me, at least, it seemed like the quietest 17 homers ever, but ESPN’s Home Run Tracker disagreed. It classified 3 of the bombs as “No Doubters”, 10 as “Plenty”, and just 4 as “Just Enough.”

For your viewing pleasure, here is his longest home run of 2015, hit off the Marlin’s Brad Hand on August 15.

He posted a .218 ISO in the Minors, he pulls the ball with authority, he hits it hard—you get it, the power checks out. Young power usually comes at the expense of batting average, but Grichuk posted a healthy .276 AVG over 350 PA last season.

The catch with Grichuk seems to be that his “healthy” 2015 batting average (Sorry I used that word, what does that even mean? I’ve just read it before and am brainless) was a mirage. When your AVG is just four points higher than your ISO, either your power is off the charts, or something cooky is going on. That something cooky in Grichuk’s case is BABIP. (That stands for batting average on balls in play, i.e. how many balls did you hit fair that did not result in an out?). Out of curiosity, I made this chart which yielded somewhat interesting results.

After compiling a .299 BABIP across five seasons in the Minors, Grichuk magically posted a .365 mark in his rookie season. For someone who also struck out 31.4% of the time, that is not sustainable in any way. Here’s a pie chart of his plate appearances that explains it intuitively.

If you tack on his 6.3% walk rate and his 10.1% infield fly ball rate to his 31.4 K%, you’re left with 186 of his 350 total plate appearances that yielded balls in play that had a chance to result in Grichuk getting on base. That slice of the pie is labelled “Useful Balls in Play.” Somehow, Grichuk managed to post a .365 BABIP despite not even putting the ball in play in almost half his plate appearances. Even with his above average speed, he’s not sneaking that one past the baseball gods again.

We can turn to advanced stats to shed some more light on this. xBABIP is an metric devised by Alex Chamberlain that uses batted ball variables that correlate with BABIP such as LD%, FB%, IFFB%, Spd, Hard%, and Oppo% to calculate a player’s expected batting average on balls in play. The basic idea is that by looking at the stats that should be driving BABIP, you can get a better idea of what a player’s BABIP should be.

Rotograph’s Mike Podhorzer recently looked at 2015’s xBABIP overachievers—the hitters with the greatest difference between their xBABIP and BABIP—and Grichuk ranked fifth on the leaderboard with a difference of 0.055. Mind you that leaderboard also includes Kris Bryant, Miguel Sano, Bryce Harper, and Nelson Cruz, and xBABIP is an experimental stat, I wouldn’t put too much stock in it.

So to sum up, don’t expect the sophomore edition of Randal Grichuk to pair his power with a shiny batting average and OBP. Steamer knows this and is projecting him for a .249 AVG, but a lower average wouldn’t surprise me.

Still, Grichuk has phenomenal power, and has shown the ability to adjust at a Major League level. He made improved against all pitch types from 2014 to 2015, including huge jumps against fastballs and curveballs, and the K/BB rate should improve gradually as he gains experience against big league pitchers.

One interesting tidbit that might not mean much is that Grichuk displayed strong reverse splits in 2015. Meaning as a right handed hitter, Grichuk fared better against right handed pitching than against lefties. While he did have almost twice as many at bats against righties, Grichuk hit 11 of his 17 dingers off them. He slashed an OK .265/.297/.522 v. LHP and an elite .281/.345/.562 against RHP. The trend doesn’t extend back into his Minor League statistics, but it’s something to watch.

Grichuk will be a valuable outfielder for St. Louis next season, but nobody should expect him to replicate his rookie season. That said, he’s not a household name, and his power explosion went relatively unnoticed, so if you’re a fantasy baseball player like myself, he could be still a bargain on draft day.

Steamer is projecting Grichuk for .249/.295/.445 with 21 HR, 70 RBI, 7 SB and a dramatically decreased .196 ISO over 532 PA. That feels about right to me, and heading into Spring Training, I would value Grichuk close to Kole Calhoun in the outfield.