A month and a half ago, Yasiel Puig was struggling. In the playoff series against the Cardinals, Puig struck out seven times in a row at one point, and there was a pretty clear book on him: try to beat him with heat, away. He was having trouble catching up, so the Cardinals were having less trouble putting him away, and that’s among the reasons the Dodgers were unable to advance. Anyway, nevermind the bigger context. Nevermind the Dodgers. It’s interesting how Puig was being pitched.

Because the book on Puig late in 2014 was sort of the opposite of the book on Puig late in 2013. A year ago, it seemed like pitchers solved Puig by busting him with fastballs inside. That was the scouting report at the time, and there’s no reason to think it wasn’t valid. It’s just, accurate scouting reports can be temporary scouting reports, sometimes. Over the course of 12 months, Yasiel Puig changed his own book.

We ought to reflect on a couple things. From Dylan Hernandez, in spring training:

Puig batted only .214 in September of last season, convincing scouts from opposing teams they discovered how to attack him: By pounding him inside with fastballs and throwing off-speed pitches away. Puig said he is making adjustments and if he fails to produce at the same level he did in his rookie season last year, it wouldn’t be for lack of effort.

From Jorge L. Ortiz, in spring training:

The focus instead is on him adjusting to pitchers after they seemed to solve Puig late in the season, attacking him with fastballs inside and limiting him to a .214 batting average in September. “I’m working on my hitting and on the things that may hurt me, with how smart the pitchers are,” Puig said. “I’m working on the pitches I missed last season and on the areas where I’m uncomfortable.”

It’s all well and good to say you’re going to do something. Pitchers will talk about how they’re smoothing out their mechanics, or picking up a third or fourth pitch. It’s quite another to actually successfully do something, and with that in mind, I want to highlight a comment left here by MGL a week and a half ago:

You CAN however infer to SOME degree a batter’s “strengths and weaknesses.” It is the percentage of time he gets a pitch, compared to other batters, again, given the same context. If batter A gets a high, inside fastball 30% of the time, and batter B, 28% of the time, assuming the exact same context, then we can assume that batter A is weaker with that pitch than batter B, relative to the other pitches and the overall value of all pitches to that batter.

Results get spoiled by context. The best way to get a guy’s scouting report is to read his actual scouting report. We can’t do that, but we can use a workaround: we can look at how a guy gets pitched. We can look, even independent of results. The more a guy gets pitched a certain way, the more confident we can be that’s highlighting what’s perceived to be a weakness in his game. It’s not perfect, but it’s the best we can do, just about.

So, data, courtesy of Baseball Savant. I looked at right-handed batters who faced at least 1,000 pitches. I narrowed down to fastballs over or beyond the inner half of the plate. A year ago, Yasiel Puig saw inside fastballs on 40% of his pitches. This was the second-highest rate, less than half a percentage point behind Matt Holliday. The average was 28%. Based on the way he was pitched, Puig presumably had a weakness against inside heat.

Now turn to this past season. The average, again, was about 28%. The leader, again, was Matt Holliday, at about 39%. We find Yasiel Puig at 32%. It’s still a higher mark than the average, but that represents a significant drop. Once every 13 pitches, on average, what was an inside fastball turned into something else. What’s implied is that Puig did pretty well at correcting his first big-league weakness. If nothing else, it’s at least no longer so weak.

For context, 110 different right-handed batters saw at least 1,000 pitches in both 2013 and 2014. Puig’s inside-fastball rate dropped by eight percentage points, the biggest drop by two full percentage points over Brian Dozier, who changed his own batting profile. No one else had a drop bigger than five percentage points. For the record, Allen Craig saw the biggest increase, of seven percentage points. This isn’t surprising, as something happened that sapped Craig’s bat speed and pull power.

What if we change the denominator? How about, instead of inside fastballs over all pitches, we look at inside fastballs over all fastballs? In 2013, 67% of fastballs to Puig were inside. In 2014, that dropped to 52%. Here are the two biggest drops:

Yasiel Puig, -15%

Tyler Flowers, -7%

(By this measure, Alex Rios had the biggest increase, of ten percentage points.)

Puig’s drop wasn’t just baseball’s greatest — it was the greatest by more than double the runner-up. It’s about as strong as evidence gets that the book on Puig changed season to season. There’s nothing so obvious we can observe about Yoenis Cespedes after he first appeared. Puig changed by a highly unusual amount, at least based on how pitchers chose to approach him.

You might be a visual learner. Here’s a fastball heat-map comparison, from Baseball Savant:

Here’s a fastball location comparison, from Brooks Baseball:

Different, those images. They just back up what the numbers were already saying. Most batters get pitched similarly season to season. Puig’s profile underwent a significant change.

Which is not to say that Puig simply eliminated a hole. In working to get better against inside fastballs, Puig subsequently opened himself up a little more against fastballs away. It’s hard to protect against all pitch types in all pitch locations, and adjustments tend to have consequences. So now Puig has just changed the distribution of his weaker areas. But between years, he set his mind to getting better against something, and it appears he mostly pulled it off. That’s not something we often observe, which is what makes this so interesting. There’s a book on every player in baseball. Generally, the book doesn’t change very much over the course of a handful of years. But sometimes things can change in a hurry, and an adjusted book becomes needed. The book on Yasiel Puig responded to Puig’s response. We’ll see what Mike Trout’s future holds against fastballs upstairs.