A deep dive into Patrick Bailey's second-half offensive struggles for the Giants

Patrick Bailey gets tired in the second half of the season, and that’s why he slumps.

This is less of a hypothesis and more of a generally accepted truism. When I squat for 30 seconds, I have to take a week off work. Bailey squats and squats and squats for several months, so it makes sense that his hitting mechanics are affected in the second half. Without power from his base, he’s unable to start the kinetic chain and get his bat through the zone as quickly. It’s a simple, intuitive explanation.

And if there’s one thing I hate, it’s simple, intuitive explanations. Let Occam toss his razor and grow a beard. What are we, the Yankees? Let’s confirm this truism before accepting it and and anticipating it every season. Might be correct. Seems like it’s correct. But is it?

First, let’s go back to the part where it makes perfect sense that catchers get tired over a long, long baseball season. The position is the most demanding in baseball, if not sports. Even with regular rest, wear and tear seems inevitable.

That’s easy enough to check. Here’s what catchers did in the first half of last season compared to the second half:

Looks like a negligible difference. And it’s not like only catchers have to deal with the marathon of a baseball season. So let’s see if there’s a difference for all of the other positions.

If catchers are worse at hitting in the second half than the general population, it’s by a teensy amount that’s indistinguishable from statistical noise. That’s not true for Bailey, though. The differences are as extreme as you’ll find in the sport for any split. In the first half, Bailey is a latter-day Buster Posey. In the second half, he hits like a pitcher, and not one of the good ones.

There’s a stat called tOPS+ that compares a player to himself in a chosen split, and Brandon Belt is probably the easiest player to help explain this stat. In 2018, he had an .822 OPS against right-handed pitchers and a .628 OPS against left-handed pitchers. His tOPS+ against righties was 117, which means his production was 17 percent better against right-handers than his season total against everyone. His tOPS+ against lefties was 68, which means his production was 32 percent worse than his season total. A lower number means the player is worse in that split compared to his overall numbers, and higher means he’s better.

Since 1958, Bailey’s 37 tOPS+ this season in the second half was the fifth-worst in all of baseball for any player in any half. Just four players were a worse version of themselves in one half of the season compared to the other. Bailey’s 62 tOPS+ in the second half of 2023 was only the 208th worst difference … but, again, we’re talking about all of baseball over a span of 66 seasons.

It’s not just fans and writers who are noticing the stark difference either. Bailey added 20 pounds (the good kind) last offseason specifically to help him avoid the second-half slump from his rookie season. It was a priority for him, and the results were even worse. Maybe this is just how it’s going to be.

Except, hold on, what makes Bailey so much worse in the second half compared to his peers, who also have to squat, take foul tips to the body and block balls in the dirt all season? It’s not a problem for most catchers. Heck, when Posey came back from his broken ankle, he was supposed to fatigue quickly because of the year off, except he had one of the greatest second halves of any catcher in history. There’s no evidence that catchers are generally worse in the second half. So why just Bailey?

First, look for evidence of fatigue. Does his bat speed slow down? Does he see more fastballs because he’s unable to catch up with them? Does his swing get longer as the season progresses?

No, no and no, respectively. Against fastballs over 95 mph in the first half, Bailey hit .171/.237/.371. In the second half, as miserable as it was, he made more contact against the fastest fastballs, hitting .258/.378/.323. If fatigue is the culprit, it’s not showing up in his ability to hit high velocity, which is where you would expect. It’s possible that he’s cheating against velocity to catch up, which leaves him vulnerable to off-speed and breaking pitches, but he’s also better against fastballs in general.

Another thing that doesn’t make sense: If Bailey is too fatigued to hit as well as he did in the first half, it would follow that he’s too fatigued to catch as well, too. Except that wasn’t the case; his metrics were steady. FanGraphs had Bailey being almost twice as valuable defensively than the second-best fielder in baseball — take a second to process every one of those words — and one doesn’t get that far ahead by pooping out over the last couple months of the season.

The more data there is to dig through, the more likely that the most important number is this one: 184. As in, that’s how many plate appearances Bailey had in the second half of the season. That’s a sample that’s too big to ignore, but too small to trust. A lot of funny things can happen in that many PA. Armando Ríos had a .947 OPS in 177 PA in 1999. Rick Wilkins, a catcher, had an .876 OPS for the 1996 Giants in 183 PA, all of them in the second half. Freddy Sánchez had a .619 OPS after getting traded to the Giants in 2009; he helped them win the World Series the next season.

If you dig even deeper, you’ll see that Bailey’s second-half numbers are so bad because of a single month. In September, he hit .266/.324/.359, which isn’t great, but also not awful. It’s perfectly fine, especially for a Gold Glove catcher. In August, though, Bailey hit .063/.090/.078 in 67 PA. That was …

• The fourth-worst batting average for any month by a player with more than 60 PA in the history of baseball.

• The third-worst on-base percentage for any month in the history of baseball.

• The fourth-worst slugging percentage for any month in the history of baseball. Also, everyone ahead of him played before 1910, when balls were made out of potted meat and glyptodon shells.

It was the worst offensive month by any player in modern baseball history. Then he was mostly fine the month after that. You can choose to believe that all of this was due to fatigue, which wouldn’t explain why he improved in the final month of the season, but I’ll give you one more set of numbers before you make up your mind: .191/.226/.330. Those are Bailey’s expected statistics in the month of August. They’re bad numbers. But they’re not historically awful. They’re the kind of numbers that indicate a bad month, nothing more. It’s the kind of bad month that almost any hitter is capable of, regardless of how fatigued they are. And just for good measure, Bailey’s exit velocity was higher in August than it was for the entire season.

Mix in a regular-bad month with his second-half numbers and you have a generic slump. Maybe the narrative about Bailey’s second-half fatigue is still there, but it’s more of a suspicion than a truism.

My personal theory is this: Bailey was indeed tired in the second half of his rookie season, getting used to catching every day in the majors during a season that was a month longer than any he’d played before. He also had a miserable second half of his 2024 season, with most of his ineffectiveness coming in a single month. But the two don’t have to be related. The two don’t have to be predictive. First- and second-half samples fluctuate wildly and unpredictably for almost every stat, and I can’t find evidence that Bailey is somehow doomed to suffer the same fate in every second half just because it happened in consecutive seasons.

Fool me once, shame on those stupid numbers. Fool me twice, more shame on those stupid numbers. Fool me a few more times, and we’ll definitely have to admit that something weird is going on. Right now, though, Bailey’s second-half slumps seem more like hiccups than truisms.

(Top photo: Rob Carr / Getty Images)