Remember when Ryan Mountcastle couldn’t take walks?

It was the fourth inning of the Rays-Orioles matchup last Saturday, and Ryan Mountcastle was facing the right-hander Michael Wacha, one of the league’s better control pitchers, with a 4.5% walk rate last season ranking in the top seven percent of MLB pitchers. Mountcastle quickly went down 0-2, swinging through a curveball and a changeup, then laid off two balls, including a 96-mph fastball that missed upstairs. The rookie then fouled off three pitches in a row, took a second curveball in the dirt for ball three, fouled off 95 inside, fouled off an 88-mph changeup, then took a cutter low-and-away, the first cutter Wacha had thrown him, for ball four. All in all: 11 pitches thrown, Wacha’s entire arsenal on display, and Mountcastle had earned himself a free pass.

The Orioles ended up wasting this impressive effort, but the numbers don’t lie: Ryan Mountcastle has been the Orioles’ best hitter since the All-Star Break, thanks to a major mid-to-late-season offensive burst. Over the past 28 days, Mountcastle has a .310 average and he’s OPS’ing 1.060 with eight home runs and 16 RBIs, and his month of July was arguably even better. What’s fueling that offensive improvement? Well, part of it is that the rookie is getting choosier with his pitches.

There have never been any doubts as to who Mountcastle is as a hitter: a dude with plenty of thump and not the greatest plate discipline. For all his offensive chops, Mountcastle has never walked much. Even in 2019, the season he won International League MVP honors with Triple-A Norfolk, his 4.3% walk rate was the fifth lowest of any upper minors player with at least 500 plate appearances. In 2020 as a rookie with Baltimore, Mountcastle walked 11 times in 140 plate appearances—an improved 7.8% rate, but still just at-or-below average for major league hitters, and one people weren’t sure if he could sustain over a season.

Mountcastle started off the 2021 season ice cold at the plate. He hit below .200 in April with a team-leading 40.9% strikeout rate. He walked just seven times in his first 188 plate appearances, a lowly 3.7%. He chased offspeed pitches outside the zone at a shocking 60%.

But my, how our rookie has come along since then. Since June, Mountcastle has racked up walks at a career-best 8.7% rate, never falling below 7.3% in any subsequent month. In June, he walked seven times over a five-game stretch, something he never did once in the minors. These walk rates aren’t exactly threatening Joey Gallo’s league-leading 23.2%, but all the same, this is a huge improvement for the free-swinging slugger.

Yes, Mountcastle still chases too much: his chase rate of around 40% is the seventh highest chase rate of any hitter in baseball, and it’s stayed consistent month-to-month this season. However, Mountcastle is being selective in a different way. He’s swinging at pitches in the zone more often than any other hitter in baseball, 86.4%, and a full 10% more than he did during his early-season slump. The approach seems to be working: over the season, he’s gotten more and more pitches in the strike zone. This is a virtuous cycle at work: when Mountcastle shows more patience at the plate, he gets better pitches to hit. More strikes, more swings, better contact. You get the idea.

Encouragingly, Mountcastle’s batted-ball numbers back this up—a pattern Orioles stats wizards must be delighted to see. The below chart shows Mountcastle’s offensive splits by month in 2021.

As you can see, June was a good month for Mountcastle, but so was August and the first day of September. In fact, his slugging and WOBA were better in August than any other month. And his walks have been pretty consistent, month-to-month, since he busted out of his early-season slump.

As for contact, there are some very good signs. July was something of a down month for Mountcastle. But this seems partly due to his missing time with a concussion, and partly due to bad batted-ball luck. Moreover, his barrel percentage barely dropped at all that month, while his swing-and-misses continued to decline on a monthly basis. In short, it’s been a good long stretch where Mountcastle has been making quality contact, even where the immediate results didn’t show it. The conclusion: a good approach.

It would be great if Mountcastle were a sort of canary in the coal mine for this team. Pitch discipline remains a big issue for the Orioles, who as a whole have the third-highest chase rate in baseball. But as the Baltimore Sun’s Jon Meoli noticed, Mountcastle’s improvements in plate discipline are consistent with the lessons the Orioles are trying to inculcate up and down the farm system: Choose your spots. Don’t expand the zone. Hit the ball hard. So far, the results suggest that, for O’s minor leaguers, these instructions are working. Now, if even the swing-happy Mountcastle can learn to take some walks, then perhaps the rest of the Orioles can, too.

Folks say you can’t teach speed, and you can’t teach talent. There’s no doubt that Mountcastle’s ability to thwack the ball hard is his and his alone. But it’s great to see signs that the Orioles’ new hitting philosophy may be trickling up to the bigs, and with some already impressive results.