Major League hitters have embraced launch angle in recent years, realizing that driving the ball in the air more frequently can unlock power and create success.
But like with anything, there are limits. Joey Gallo's 2017 season is one example.
The Rangers slugger was a solid performer at the plate in the first half, batting .194 but slamming 21 home runs and posting an .821 OPS. In the second half of his age-23 season, however, Gallo was a star with the bat, slashing .229/.357/.572 with 20 more homers.
The Statcast™ metric of expected weighted on-base average (xwOBA) gives the hitter credit for the quality of his contact, as well as his actual strikeouts and walks. After the All-Star break, Gallo's .412 xwOBA ranked seventh in the Majors (minimum 200 plate appearances), just ahead of Anthony Rizzo, Michael Trout and Josh Donaldson. Focus only on balls put in play, and Gallo's .610 second-half xwOBA -- about 100 points higher than his first-half mark -- edged out Aaron Judge for the MLB lead.
So what made the difference for Gallo after the break?
He did walk a bit more and strike out a bit less, but neither changed dramatically. His average exit velocity and rate of hard contact -- both of them among the best in the game -- barely budged. On the other hand, Gallo's average launch angle declined from an MLB-high 25.6 degrees to a more modest 19.3 degrees.
More illuminating than Gallo's average launch angle is the breakdown of how often he made contact in certain launch-angle groupings.
Because he hits the ball so hard, Gallo's range of effective launch angles is wider than most. For example, MLB hitters as a group batted .130 and slugged .349 on launch angles between 35 and 45 degrees in 2017, compared with .336/.562 on all batted balls.
Gallo, however, managed to go 10-for-34 (.294) with eight homers and a 1.059 slugging percentage from 35-45 degrees. This 111.9 mph, 44-degree moonshot off the Mets' Jacob deGrom on June 6 illustrates this point.

But even Gallo has a ceiling. On batted balls hit above 45 degrees last season, he went 1-for-46 with a pop-fly single. In other words, these batted balls are virtually automatic outs, and Gallo cut down on them considerably after the break.
Gallo's first half:
• 31 batted balls above 45 degrees
• 22.8 percent of his total batted balls
• Third-highest rate among 302 batters (minimum 100 batted balls)
Gallo's second half:
• 15 batted balls above 45 degrees
• 12.8 percent of total batted balls*
• 88th-highest rate among 263 batters (minimum 100 batted balls)
*MLB average: 11 percent
Where did those extra batted balls go? Mostly, to a more favorable range of launch angles.

Gallo's first half:
• 26 batted balls between 0-20 degrees
• 19.1 percent of total batted balls
• Lowest rate among 302 batters (minimum 100 batted balls)
Gallo's second half:
• 35 batted balls between 0-20 degrees
• 29.9 percent of total batted balls*
• 120th-highest rate among 263 batters (minimum 100 batted balls)
*MLB average: 29.3 percent
On this collection of ground balls and line drives, Gallo went 34-for-61 (.574) and slugged .836 in 2017, despite producing just one home run.
Gallo's optimal launch angle is a bit higher -- 34 of his 41 big flies left the bat at between 25-40 degrees -- but these results still dwarf what he did in the 45-plus degree range. Take this controlled swing that turned an 0-2 pitch from Astros left-hander Francisco Liriano into a 15-degree, opposite-field RBI single on Aug. 30.

Gallo will enter his second full big league season with confidence and the knowledge that he has a spot in the Rangers' lineup. Still, talk of his strikeouts will continue into 2018, coming off a year in which he had the second-highest K rate and highest whiffs-per-swing rate among qualified hitters.
That's fair, but Gallo's lack of contact isn't the only thing worth considering. It's also a matter of how much of the contact he does make is of the harmless fly-ball variety -- something that is barely more valuable than a strikeout.