Home runs are loud but noisy — a hitter can homer on a mistake or get robbed of three. Power analytics look underneath the results at the quality of contact, so you can tell real power surges from lucky streaks.
Barrel %
A barrel is a batted ball hit with the combination of exit velocity and launch angle that historically produces the best outcomes — think high average and slugging on contact. Barrel% is the share of a hitter's batted balls that qualify. It is the gold-standard power indicator because barrels translate to damage more reliably than raw home run counts, which bounce around with park and weather.
Hard-hit %
Hard-hit rate is the percentage of batted balls hit at 95 mph or harder. It's a broader, more stable measure than barrel% because it captures all authoritative contact, not just the optimal launch-angle window. A hitter with a rising hard-hit rate is squaring the ball up more often — the raw material of power, even if the launch angles haven't fully clicked yet.
Exit velocity
Exit velocity is simply how fast the ball leaves the bat. Average exit velocity and top-end exit velocity both matter: the average speaks to consistency of contact, while the peak speaks to raw power ceiling. Exit velocity stabilizes quickly, which makes it a useful early read when the sample of games is still small.
xSLG — expected slugging
Expected slugging percentage estimates what a hitter's slugging should be based on the quality of their contact — exit velocity and launch angle — rather than where the balls happened to land. When a hitter's actual slugging trails their xSLG, they may be hitting into bad luck and due for positive regression; when actual outruns expected, the production may be running hot. The gap between the two is one of the most useful tells in power analysis.
Reading a trend, not a snapshot
The point of a power trend is comparison over time. A single season-long number hides what a hitter is doing right now. By comparing a full-season baseline against a recent rolling window — the last month, say — you can see whether the underlying batted-ball quality is genuinely rising or fading:
- Recent barrel% and hard-hit% up vs. season: a real power surge, even if the home runs haven't all shown up yet.
- Home runs up but batted-ball quality flat: likely a hot streak riding park, weather, or luck — treat with caution.
- Quality up but results flat: a hitter potentially due, especially if xSLG outruns actual slugging.
Why power trends matter
Power is streaky on the surface but its inputs are far more stable. By tracking barrels, hard-hit rate, exit velocity, and xSLG instead of just home run totals, you catch power coming and going a step early — and you avoid chasing a hitter whose recent long balls were really the ballpark's doing. Pair a power trend with the park and weather environment for the complete picture.
Sample size and stabilization
Not all power metrics settle at the same speed, and knowing which to trust early is half the battle. Exit velocity and hard-hit rate stabilize relatively quickly — a few dozen batted balls start to tell a real story. Barrel rate takes a bit longer, and home run totals themselves are the slowest and noisiest of all. That ordering is exactly why quality-of-contact metrics lead results: they give you a trustworthy read on power while the home run column is still catching up. When a rolling window is very small, weight the fast-stabilizing inputs and treat the raw home run count with caution.
xSLG vs. xwOBA
xSLG is power-specific — it estimates slugging from contact quality. Its cousin xwOBA (expected weighted on-base average) is broader: it folds in walks and all types of expected outcomes to describe a hitter's total offensive value, not just power. For a pure power read, lean on barrel%, hard-hit%, and xSLG; when you want the complete hitter, xwOBA rounds out the picture. Both are defined in the Analytics Glossary.
A worked read
Imagine a hitter with three home runs in his last week but a hard-hit rate and barrel rate sitting right at his season norm. The surface says 'hot'; the inputs say 'ordinary contact that happened to leave the yard,' often with help from a friendly park or wind. Now flip it: a hitter with just one homer but a clear jump in exit velocity, hard-hit rate, and xSLG over the same window. The results look quiet, but the underlying power is genuinely rising — frequently the more actionable signal of the two.
The same logic works in reverse as a cooling signal. When a hitter's barrels and hard-hit rate slip below their season norm even as the home runs keep coming for a little longer, it often marks the front edge of a downturn — the results are trailing a decline that the quality-of-contact metrics have already started to show.
View today's Power Trends →