Isolated Power (ISO) measures the number of extra bases per at bat. It's essentially slugging percentage minus batting average. Or, for a more precise formula:
(2B + 2 * 3B + 3 * HR) / AB
Getting to second base (or beyond) with your own swing of the bat is what builds your ISO. Stolen bases don't count. Nor do well-placed bunts, sacrifice flies, or run-scoring GIDPs. Or singles.
Through May 28, the Royals had a team ISO of .097. Since 1977—the year the American League first expanded to 14 teams—only five American League clubs have had a team ISO below .100. Four of those were in 1981, which is a special case. Studies have shown that the ball carries better in warmer weather, and the 1981 players' strike that cancelled two months of games in the middle of the summer made for low ISO all around. In 1981, four AL teams (but not the Royals!) would end the year with an ISO below .100.
Since then, only the 1992 California Angels have finished their season with a team ISO below .100. Third baseman Gary Gaetti led the team with just 12 home runs, and center fielder Junior Felix led the team with 22 doubles and five triples. The Angels lost 90 that year, and tied with the Royals for fifth place in the AL West.
A high ISO does not guarantee a playoff spot, and a low ISO does not guarantee a losing season. The 1969 New York Mets won 100 games—and the World Series—despite a team ISO of .109, and the 1996 Detroit Tigers lost 109 games despite an ISO of .165.
Generally, though, a high ISO is better than a low one. Of the teams that recorded the 25 lowest ISOs since the year of those Amazin' Mets, only three had winning records, and only one made the playoffs. Of the teams with the 25 best ISOs since 1969, 19 had winning records and eight made the playoffs. (A ninth, the 1994 Cleveland Indians, was in a good position for a wild card spot if the end of the season had not been cancelled.)
Since the Royals began play in 1969, their lowest team ISO has been .098, set in their inaugural year and again in 1972. If the Royals continue their current pace, they'll have the lowest ISO in franchise history. But we know they're all going to improve, right?
But we only know part of the story if we look at a team's ISO in isolation. To see the full picture, we need to look at the team's ISO in comparison to the rest of the league. The 1927 New York Yankees' .182 team ISO looks impressive, but it's even more impressive compared to the league average of .114 that year. On the other hand, the 1999 Minnesota Twins' team ISO of .120 would have been a solid performance in the deadball era, but pales in comparison to 1999's league average of .165.
In the Kansas City Royals' entire history, the team has had a better than league average ISO six times.
In three of those six years, the Royals won their division, and in two others they won at least 90 games. In 1977, their best year by far in terms of ISO, the Royals had six players with 16 or more home runs, and three with more than ten triples. Hal McRae set a team record and led the league with 54 doubles. The team won 102 games.
In 1975, John Mayberry hit 34 home runs and 38 doubles, and led the league in OPS+. He also led the league in walks, partly because pitchers feared to throw him strikes.
1985 was the year of Steve Balboni’s legendary 36 home runs. George Brett added 30 more, and even Frank White hit 22. Willie Wilson led the league with 21 triples. It was also, of course, the year of the last Royals’ playoff appearance, a World Series victory over the Cardinals. Good things can happen when you hit the ball hard.
Now I’m going to list the Royals’ six worst years, in terms of underperforming the league average ISO.
Several things stand out in this chart:
Among these six years, only 2013 was a winning season.
The gap between the Royals and the league average is much greater in their worst years than in their best. That's perhaps inevitable when there are 37 below-average years to pick from.
The Royals' ISO in 1996 and 2000 compares favorably to their ISO in 1975 and 1978, unless you look at the league context.
That .098 ISO in their first season was bad, but it wasn't as bad, in context, as last year's result.
So how does this year's team stack up?
|2014 (through 5/28)||.097||.141||-.044|
So we can’t fully blame the lack of power on the early-season weather. While most teams are still below last year's numbers, they're not as far below as Kansas City is. The Royals are on pace to have not only the lowest ISO in team history, but also the greatest gap between themselves and the rest of the league. This is not news to anyone who follows the team.
What ISO does show us, because it measures all extra base hits, is that the Royals' power struggles go far beyond hitting it out of the park. Kauffman Stadium is not a great park for home runs, but historically the Royals have made up for it with gap power. As recently as 2012, Alex Gordon led the league with 51 doubles. But last year and this, the Royals simply have not gotten extra base hits like they have in the past.
We can make jokes about the singles train, and the front office can offer excuses until they're royal blue in the face. The numbers don't lie. Since the beginning of 2013, this team has lost its ability to get extra base hits.