Early June Isolated Power (ISO) for fantasy baseball: the top 100

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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, Manny Machado has a .593 slugging percentage and .308 batting average, which gives him a .285 ISO.

According to research done over at Baseball Prospectus, ISO stabilizes around 160 at bats. Now into June, most hitters have crossed that threshold. Here are the top 100 batters in ISO and their differentials from last season. MLB average ISO is .157 in 2016.

David Ortiz is having the greatest offensive age 40+ season ever. His wRC+ sits at 200 as of this afternoon, 63% higher than Willie Mays' 157 wRC+ in 1971, the next closest to Ortiz. To keep this pace up would be well beyond anything Ortiz has ever put up in a season. His best wRC+ was 175, in 2007. Ortiz will almost certainly regress going forward, but will likely still end up among the best in the game by seasons end.

This is now Yoenis Cespedes' 5th year playing baseball in the big leagues. He's been a completely different hitter since coming to the Mets in August of last year. His ISO is about 70 points higher than last year's .251, which was seen as a career year type of performance. It's possible Cespedes is just timing up MLB pitching better in his 5th season, and we can reasonably expect a significantly elevated level of performance from him going forward.

Jay Bruce appears to be over some injury problems the last few years and is having the best offensive season of his career. His start to 2016 is comparable to his 2012 season, where he finished with a .281 BA and 25 HR.

Robinson Cano has had a monstrous bounce back year for power after playing most of the first half of 2015 with a stomach illness that apparently zapped his power. Adjusting for run scoring environment, Cano is having a season similar to his peak 2012 season with the Yankees. This doesn't mean the same for fantasy purposes, because Yankee Stadium is a much more hitter friendly environment than SafeCo, but it does show that Cano's skills are not eroding like we may have feared last year.

Bryce Harper being ranked #13 in ISO yet having his ISO differential be -.47 says more about how great his 2015 season was than anything else. Harper is seeing less first pitch strikes than ever before and likely isn't getting a whole lot of good pitches to hit.

Evan Longoria's power output looks a lot like his vintage years, with ISOs over .230 routinely. His home run to fly ball rate (15.4%) is about what it was in 2013, too, the last of his peak seasons.

I traded Mookie Betts last year at the trade deadline in my keeper league in a win now move for Chris Archer and David Ortiz. I could only keep Ortiz based on my league rules. I don't regret it, because the move helped me win a title, and flags fly forever. I also traded him around the time he had his concussion, and I never saw this type of power output coming from him. Betts already has 14 HR, just 4 less than his 2015 total. He's one of the best young players in baseball.

Giancarlo Stanton is a mess, and I'm not sure what is going on. He is striking out 34% of the time, which is scary high. I wonder if this is at all related to some sort of delayed effect from getting hit in the face in 2014, but that is just reckless speculation without much substance. He is just 26 years old, it is strange to see a Hall of Fame type talent fall apart like this.

Daniel Murphy is a fundamentally different hitter after making mechanical adjustments in the second half of last season with the Mets. He is no longer a mediocre hitter. He is legitimately a top hitter in the game right now. Murphy has a .492 BA on ground balls, which will come down as the season goes along, but he's striking the ball well on grounders based on launch angle + exit velocity measurements, so he appears to be able to sustain a well above average BA on ground balls.

Jonathan Lucroy has had a huge bounce back year after struggling with a concussion last year. 2015 can probably safely be chalked up to a fluke year because of the brain injury. He has resumed his place as one of the top fantasy catchers.

Jose Altuve is hitting for way more power while keeping his stolen base skills and high batting average. He is now walking at a 10% rate and is seeing significantly less first pitch strikes. He is a legitimate top 5 player.