BOSTON — It is accurate to say Rick Porcello has returned to form, but only in a broader sense. What’s powering Porcello's 2.23 ERA is a different pitch mix than he had in his 2016 Cy Young season. And the results thus far have been even better than the ones he found in his banner year.

Porcello threw hard stuff, a four-seamer or a sinker, about 60 percent of the time in each of the last two seasons, per BrooksBaseball.net's tracking. This year, that’s down to 50 percent, with a heavy increase in both his slider and changeup.

Pitch mix, of course, doesn’t matter if everything is over the plate. To that end, Porcello’s command appears universally improved.

Image Courtesy of BrooksBaseball.Net

In 40 1/3 innings through six starts, Porcello has walked just four batters and allowed only one home run. A year ago, he allowed 38 homers in the regular season, most in the majors. He's walking batters half as often as he did last year.

“They both have been a focus of mine coming into the season,” Porcello said after his no-decision Sunday in a 4-3 win over the Rays. “Limit the damage, not give up the extra-base hits, the doubles and homers. Both of them are important for me. I'm not going to go out there and punch out 10, 12 guys a game, so I've got to keep guys off base and limit damage and hits best I can. I want to keep excelling in both those categories.”

Porcello has long been known for intensive preparation. A lot of the plan he's executing now began in the offseason. With the changeup, in particular, pitching coach Dana LeVangie noted a slightly lower arm slot may be beneficial.

“Going over things in the winter before I actually talked to him,” LeVangie said, “his percentage of [changeup] usage was down from previous years, and I felt like we had to get back to it. But I also didn’t like the way he was throwing it last year. He's just throwing it with far more conviction right now. And you know, a lot of it goes back to his commitment on trying to get better each time. Has really helped it.”

The changeup, often referred to by manager Alex Cora, is being used more heavily than at any point in Porcello’s Red Sox career. Last year, he threw it 9 percent of the time. The Cy Young year: 12 percent.

Now, Porcello is throwing the change 16 percent of the time, nearly doubling last year’s frequency. Opponents have a .207 average against it this year. A year ago, they were ripping it, to the tune of .325.

The off-speed offering is crucial down in the zone for keeping barrels away from his sinker.

“You can’t have success in areas of the strike zone if you don’t use your other pitch mix in those locations,” LeVangie said, “and he has done a really good job."

Even more effective in 2018 is Porcello’s slider, which has a .130 average against. Unsurprisingly, he’s throwing that pitch more than he has at any point in his career, a quarter of the time.

Two years ago, Porcello favored the curveball more than the slider, and their usage was about equal in 2017.

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More than most pitchers you'll find, Porcello's seemingly in a state of constant flux.

Throughout the righty’s career, Porcello has been referred to as a sinker baller. That has not always been accurate, however: he’s moved between usage of his four-seamer and his sinker. The sinker has not always been the driving force. Indeed, finding the right balance of hard stuff has appeared a start-to-start task in his career.

“He always struggled between, is he a sinker ball pitcher or can he be … a power pitcher,” Alex Avila, Porcello's former catcher in Detroit, once said of Porcello’s early years. “He was constantly trying to find that right mix. And be able to use both. And that was something for a few years that it was just a back and forth, give and take, kind of like a trial and error. And his stuff, and his ability, his talent was so good… he was much farther along than most guys at his age.”

A year ago, Porcello threw his four-seamer and sinker nearly identical amounts, 30 percent of the time. Now, his sinker is at 35 percent, creeping back to the 41 percent mark he sat at in 2016. That's notable considering sinkers are a threatened art in today’s launch-angle era.

Meanwhile, Porcello's four-seamer is doing something of a disappearing act. He’s halved its usage in 2018.

How much does Porcello trust his sinker? He's throwing it as a first pitch 52 percent of the time this year. With two strikes, you're liable to see anything but the curve. Sliders 36 percent of the time, four-seamers 23 percent, sinkers 19 percent and changeups 17.