How Pitchers Start Losing It

What Reynaldo López and Tyler Kinley reveal about the warning signs teams fear most

One of the cruelest things about pitching is how quickly it can disappear.

Velocity leaves first sometimes. Sometimes it’s command. Sometimes the breaking ball just…stops breaking the same way. A pitcher can spend years building himself into a dominant major league arm only for one small thing to slip and unravel the entire structure.

Which is why teams spend so much time trying to identify the difference between a slump, an injury, and a decline.

And right now, the Braves may be trying to answer that question with Reynaldo López and Tyler Kinley. Let’s talk about it.

The Warning Signs

This sounds odd to say, but sometimes the results don’t tell you very much. There’s just too much noise involved. A hard-hit ball could be caught by a perfectly positioned fielder, while an accidental check swing could send a soft liner over an infielder’s head for a base hit. Maybe the wind knocks down your barrelled ball and it’s caught on the warning track for an out, while another batted ball goes right down the line and leaves the park despite subpar velo.

The sample sizes are just too small to rule out the random variation that can happen to a batted ball.

The truth is not in the results, it’s in the inputs. Velocity loss, command slippage, and deteriorating bat-missing ability are the kinds of signals teams fear most…because they’re often the indicators that something deeper is wrong.

For a pitcher, the common inputs to measure are the individual pitches themselves: the velocity, their location, the degradation of their shape over time, and how much opposing batters chase and whiff at them.

What’s Happening to Reynaldo López?

López looked great in his first three starts of the year, allowing just two earned runs in 15.2 innings. His 1.15 ERA was a mirage, though - his two unearned runs and three total home runs allowed meant that his Fielding Independent Pitching was 5.11 when he was ejected for fighting LA’s Jorge Soler.

And since then, it’s been a disaster.

López made just two more starts, totaling seven earned runs on ten hits and six walks in six innings, before being moved to the bullpen by Atlanta. And things haven’t exactly been that much better out in relief - López has two earned runs in five innings, walking two against just four strikeouts with five hits (one homer).

But more concerningly, López doesn’t look like the same arm when you look at the inputs. His fastball velocity is down to an average of 92.9 mph despite the move to the bullpen, with his hardest heater since the move to relief coming in at just 95.5 mph. By contrast, he threw four harder pitches in his April 7th start alone, touching 97 mph in a strikeout of Mike Trout, and averaged 93.7 mph as a starter.

The shape of the fastball is different, too - the heater’s down to just 16 inches of induced vertical break in relief, as compared to an average of 16.6 IVB as a starter. Typically, IVB goes up with a move to relief, as does velocity, but López has gone the other way.

With the loss of velocity and shape, López is missing fewer bats than ever. His whiff rates have dropped on the slider with the move to the bullpen, while he has yet to get a whiff on a curveball as a reliever (but with an extraordinarily small sample size of just five thrown).

However, I don’t think the difference is being a reliever.

Here are those same stats, separated by his suspension after the Angels fight:

FB Velocity: DOWN 1.1 mph
FB Shape: DOWN four-tenths of an inch
Whiff rates: DOWN 5.2%

It’s hard to look at the decline across the board in virtually everything after the suspension and reach a conclusion other than some sort of lingering injury. Is it possible he injured his throwing hand when he swung at Soler? He was holding a baseball when he swung and was seen looking at the hand in the dugout after the fight wrapped up. Or is it possible that his surgically-repaired shoulder took some awkward impact and isn’t quite right?

That’s a lot less concerning than a possible realization that López has fallen off the aging curve abruptly, at the relatively young age of 32.

Tyler Kinley: A Bad Stretch or Regression?

With Kinley, it’s likely not anything as drastic as an injury or an aging curve.

No, this might be some simple bad luck.

Kinley’s first twelve appearances this season saw him allow just one earned run on four hits in eleven innings while striking out ten.

But since then, he’s been tagged for six earned runs in 6.1 innings, allowing ten hits (including three homers).

Two of the three homers have come on the slider, one last night in Los Angeles and the other last week in Seattle. The third was on a curveball in Colorado at the start of that road trip.

The two homers on Kinley’s slider have come on 30 batted balls, equaling the total from all of last year on 134 batted balls.

This is exactly the kind of small sample size noise that teams try and look past. We saw this with Raisel Iglesias last year - his slider was a problem early in the season, something we identified back in May, but most of the damage was fueled by an outlier five homers in nine batted balls.

Those five home runs on the slider was more than 2024’s one homer on 31 batted balls. And lo and behold, Iglesias normalized down the stretch. Tweaking his pitch mix to reduce reliance on the slider, Iggy pitched to a 1.34 ERA after re-taking his closer role in mid-June, including a 0.38 ERA in the season’s final two months.

When you look at Kinley’s slider from a year-to-year basis, the horizontal movement is the exact same (2.2 inches to the gloveside) and the vertical drop is within 3/10ths of an inch of IVB from last year.

Know what is different? The fact that opposing hitters are hitting it in the air at an absurd clip. Kinley’s only allowed one barrel on the slider all year, coming on Sunday afternoon on Max Muncy’s home run. He’s allowed a lower exit velocity this year than last year, at a lower launch angle, yet is already one away from last year’s homer total.

The most telling stat: Prior to statcast updating from Sunday’s game, Kinley’s 2025 xwOBA and his 2026 xwOBA on the slider are within one point of each other, actually dropping from last year’s .285 to this year’s .284.

Don’t focus on the (admittedly) poor results, focus on the pitch movement and velocity being roughly the same and attribute those homers mostly to poor locations, seemingly all of which were taken advantage of by the opponent.

How Pitchers Start Losing It

Pitchers don’t usually collapse all at once. It happens gradually, with some velocity loss here, command issues there, shape degradation creeping up, and the mistakes start increasing.

The hardest thing for teams to determine isn’t whether a pitcher is struggling. It’s whether the pitcher they knew is still in there. These two pitchers appear to be in very different places on that spectrum.

With López, the underlying indicators are difficult to ignore. The velocity is down. The shape has degraded. The whiffs are disappearing. Whether that points to injury, mechanical drift, or something more permanent, it’s the kind of profile teams start worrying about quickly.

Kinley’s situation feels far less alarming. The underlying shape and movement of the slider remain mostly intact, even if the results have spiraled for a few weeks. That’s the sort of stretch teams are often willing to bet will normalize over time.

But this is the uncomfortable reality of evaluating pitchers in-season: the line between temporary and permanent is usually only obvious in hindsight.

Pitchers rarely collapse all at once.

Usually, the signal fades slowly first.