Isolated power (ISO) is a measure of a hitter's extra base hits per at bat. It is calculated by subtracting batting average from slugging percentage. For example, Kris Bryant had a .554 slugging percentage and .292 batting average in 2016, which gave him a .262 ISO.
According to research done over at Baseball Prospectus, ISO stabilizes around 160 at bats. Stabilization is important because it gives us more confidence that the sample size is more signal than noise. All of the players below crossed past that 160 AB threshold.
Here are the top 25 risers in second half ISO, sorted by their differentials from the first half. MLB average ISO was .161 in the second half of 2016.
|Player||2nd half ISO||Differential|
Some thoughts on three intriguing players under 25 years old:
As a catcher, Gary Sanchez is probably the most captivating name on the list. The catcher position was the weakest offensive position in baseball last year, with the average catcher producing 13% worse than the league average hitter. Only one catcher finished inside the top 100 for Yahoo 5x5 scoring last year. The next lowest position was shortstop, with 12 top 100 finishers. To have a stud offensive catcher who can get some extra at bats as the Yankees DH is very appealing.
Sanchez was a good prospect, but turned into the second coming of prime Albert Pujols for his first 230 big league PAs. For some peripheral stats to back up his outcomes, his Statcast derived xOPS was an elite .984. Sanchez was legitimately a monster with his contact quality. The issue with him going forward is that it’s really hard to maintain a home run to fly ball ratio over 30% for a full season (Sanchez was at 40% last year, with a 49% ground ball rate), so Sanchez will probably have to hit less ground balls next year to keep a huge power output. I don’t know exactly where I will rank Sanchez yet this February for catchers but I will most likely have him in my preseason top 3, and can easily see him finishing as #1 after 2017 is over.
Trea Turner, like Sanchez, is another rookie who had his excellent production backed up by strong contact quality. Turner’s Statcast xOPS was .877, with a .313 xBA and .351 xBABIP, and that doesn’t take into account his elite speed, which should give those numbers a boost. Turner’s batted balls were hit at velocities and angles well constructed to cut through defenses and go for hits.
What adds to the excitement of Turner is his stolen base upside. Turner’s speed is ridiculous, and is in the handful of fastest non Billy Hamilton players in the game. He stole 33 bases in only 73 games, with an 85% success rate. The Nationals with Davey Lopes want Turner to be aggressive with base stealing, so having a base stealing philosophy stemming from the dugout will help push those SB totals higher. Turner probably isn’t a true talent .340 hitter in 2017, so he’ll have to compensate for some BA regression with more walks to sustain a high on base percentage that gives him more chances to steal bases.
Turner has a chance to be a fantasy monster with the ability to hit over .300 with pop and steal 40+ bases at the top of the Nationals lineup. His potential blend of batting average, power and elite speed is a rare and valuable fantasy asset. I’ll be interested to see what his ADP is come February, and I expect to be aggressive with Turner in my drafts and rankings.
Christian Yelich has always had plus raw power, but we hadn’t seen much of it in games until 2016. He finally started to tap into it in the second half. Yelich hit 14 HR in 275 second half AB, more home runs than he hit in any full season prior to 2016. Like the others, Yelich’s power was backed up by Statcast, with his xSLG at .473, only 10 points off his actual slugging of .483. Because of his plus raw power, I like the chances of a 20 home run repeat in 2017, and I don't think 25+ is unreasonable if everything clicks. He still hasn’t turned 25 yet.