PITTSBURGH — Trevor Williams is off to strong start to his 2018 season, sporting 1.93 ERA after his fourth start of the year on Tuesday in the Pirates’ 2-0 loss to the Colorado Rockies.

Williams’ success, on the surface, is somewhat mystifying. He’s never had overwhelming stuff, and his 4.07 ERA in 31 appearances in 2017 seemed to be more in line with what to expect for the right-hander in his second full year in the majors in 2018. In fact, ZiPS (4.58) and STEAMER (4.71) projected him to take a step back.

So far in 2018, Williams has pitched three of his four starts in miserable conditions. On Tuesday, the game-time temperature of 34 degrees matched his uniform number and he threw through persistent snow flurries. Before his first start of the season in Detroit, the California native had never thrown a pitch in the snow in his life.

“This is my third time,” Williams said. “Growing up in San Diego, there’s no snow. I went to Arizona State, the cold-weather teams come to us, and I was in the minors as a Marlin, so I was Florida State League and Southern League. I’ve just never experienced the cold weather. I’m hoping that this is going to be the last one, but it is what it is. It’s tough waking up and seeing a blizzard outside, but it’s tough for them, too.”

With the cold weather in the start to the season, Williams has seen a down-tick in the velocity of all of his pitches and has also seen his slider, Williams’ go-to breaking pitch, lack sharpness and consistency.

So he wasn’t expected to do that well this year, and the conditions have been unfavorable for him, but somehow, he’s been one of the best pitchers in the National League.

One of the big reasons that Williams has had success so far this year is the emergence of his changeup as a threat, particularly to right-handed hitters. Williams describes himself as a “fastball pitcher,” and he’s used his four-seam fastball and sinker a combined 72 percent of the time against right-handers this season. That’s actually up a bit from 2017.

But the use of his changeup has more than doubled, from 5.28 percent of the time in 2017 to 13.3 percent of the time this year. That’s for two reasons: the aforementioned inconsistency of his slider, and the fact that right-handers had a .000 batting average against this changeup coming in to Tuesday’s start.

What they’re doing with it, for the most part, is missing. The pitch had a 20 percent whiff rate against right-handers coming into Tuesday, and a 50 percent ground ball rate, to boot. It’s obviously early, and the already small early-season sample of four starts gets even smaller when deep into the cross tabs of pitch selection, but it certainly seems that the reliance on the changeup has been an intentional decision by Williams.

“It spins like my sinker, so when my arm action is good and it’s coming out right, it gets swings and misses,” Williams said. “I throw my changeup with the intention of ending the at-bat.”

That means that if he gets a swing a miss, that’s great, and if he gets a ground ball, even better. It’s the same mentality the Pirates have used for years with sinker, and that’s another pitch that Williams uses similarly. But by using the sinker to set up the changeup gives it a swing-and-miss characteristic that most of his other pitches can lack at times.

“We’ve had success doing that this year,” he said. “It’s a hard pitch to hit. It looks like a fastball. Right-on-right changeups for me are huge, because I’m known as a guy that pitches in with my sinker a lot. If we get guys singing at that sinker in, we can get swings on that changeup, as well.”

That’s why Williams still thinks the most important thing going for him is his fastball command, and the ability to put the sinker and four-seamer where he needs to.

“Everything pitches off your fastball,” he said. “I’m a fastball pitcher. I use both my fastballs to both sides of the plate and up in the zone. Really, that needs to get going for me to be effective.”

What having the changeup working does is gives him another option to turn to. Tuesday, Williams was kind of all over the place with his fastball command and his sinker didn’t have a crisp feel. The changeup gave him something to lean on when he needed an out.

“Some days, my changeup is more effective than my slider,” he said. “Some days, my slider is more effective than my changeup. Today, we kinda went with my changeup. We got some swings and misses on my slider when we needed to, but it was really sinker-changeup today.”

Some pitchers keep things simple, eschewing a varied arsenal in exchange for a singular focus on mastering a smaller selection. The Pirates’ Ivan Nova comes to mind as a player that’s pitched with just fastballs and curveballs most of his career. What Williams can bring to the table with an expanded arsenal is the innate ability to know what to throw when, in order to keep hitters off-balance.

“He’s got a feel to pitch,” manager Clint Hurdle said. “I think he showed that extremely well tonight. The changeup became a big pitch for him.”

It remains early in the year, and Williams’ 4.52 xFIP and .235 BABIP against suggest that his fortunes could experience a downturn. But it’s probably just as likely that the Californian starts to pitch a bit better when the sun starts to shine.

The Pirates came into 2018 with the rotation basically set. Joe Musgrove joined four returning members of the 2017 staff, and Steven Brault would be — and has been — the first fill-in. But beyond Jameson Taillon, there didn’t appear to be any potential stars, just a large group of roughly average pitchers. If Williams can separate himself from that pack, it would go a long way toward stabilizing the future of the rotation.

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