That's become the signature delivery of the Royals' Opening Day pitcher, taking the mound against the White Sox on Monday at 3:10 p.m. CT in Chicago.
At one time, however, the changeup wasn't even there.
Shields was a slow starter in this baseball business. Oh, he'd had a bang-up season both pitching and hitting as a high school junior in Newhall, Calif. But a stress fracture in his back scuttled almost all of his senior year at William S. Hart High, named for a cowboy movie star of the silent era. It was Shields' career that went silent, and he wasn't drafted until the 16th round of the 2000 First-Year Player Draft.
Shields pitched the 2001 season in the Minors for Tampa Bay, then there was another setback. A benign cyst was discovered in a most inconvenient place for a right-handed pitcher, his right shoulder. Surgery was necessary, and he missed all of '02.
"It could've been anywhere in my body; it just happened to be in my right shoulder," Shields said. "It ended up growing and getting enflamed, so they went in and took it out, and cleaned up some labrums and rotator cuff stuff. It just so happened it was in my right shoulder. It could've just as easily been in my leg."
When Shields came back from that mishap, something was missing: his high-powered fastball.
"After I came back from surgery, I was probably throwing 87, 88 [mph], topping out," Shields said. "So I obviously I had to become a pitcher. Out of high school, I just kind of threw a fastball and a cut fastball. I never had a changeup."
But one of Shields' older brothers, a left-handed pitcher, did have a changeup. Generous brother that he was, Jeremy shared the pitch and helped shape James' future.
Statistics show that Shields throws the changeup more than any other pitcher in the Majors.
"Yeah, I throw it quite a bit," Shields said. "Obviously, if the situation dictates, I'm going to throw it. I feel very confident in throwing it behind in the count. I'm able to command it for strikes on any count, so it's a good pitch to use."
Shields has also got his fastball, a cut fastball and what he terms a "north-to-south" curveball.
The effectiveness of a changeup depends on the way a pitcher holds the ball.
"It's just the way you grip it," Shields said. "You're not really putting both of your power fingers behind the baseball and throwing it like a fastball. You just kind of offset it a little bit, and I throw a version of a circle-changeup, but it's more of a half-circle-changeup. It's just something that as a baseball player you kind of develop."
The purpose, of course, is to make the batter think a fastball is coming but deliver it at a significantly slower speed, disrupting his timing.
"You just try to get at least six or seven mph off your fastball, or more, depending on how your changeup is," Shields said. "I like to think of my changeup as more of a power changeup. It has more movement than the speed differential. Obviously, it depends on what kind of changeup you have, but as long as it's within six or seven mph of your fastball, [which is] probably 90, 91 mph. I throw about 83 on my changeup, but sometimes it varies throughout the season."
This important pitch has taken on special significance this year for Kansas City because Shields is now the centerpiece of the Royals' rotation, having arrived from Tampa Bay in this past winter's big trade. The cost for Shields, fellow right-hander Wade Davis and backup infielder Elliot Johnson was significant -- four prospects, including the Royals organization's top hitter (Wil Myers) and top pitcher (Jake Odorizzi).
At 31, Shields is coming into what should be the zenith of his career after seven seasons with Tampa Bay. Those years produced 87 victories, a tidy 3.89 ERA and three trips to the postseason, including the 2008 World Series.
Certainly, the Royals are counting on Shields to lead them back to contention. They'd happily accept something approximating his 2011 season, when he was 16-12 and had a 2.82 ERA, 225 strikeouts and 11 -- yes, 11 -- complete games, including four shutouts.
That came after he'd had precisely zero complete games in the previous two years.
"Obviously, I had a lousy year in 2010," Shields said. "I had a meeting with [Rays manager] Joe [Maddon] before the season started, and he was telling me what he expected out of me on the year. He asked me if I had any questions. I said, 'Matter of fact, I do. I haven't had a complete game since 2008, and that's one of my goals this year -- to have one complete game.' And I ended up getting 11."
Shields found that everything was in sync -- he was keeping the ball down and getting early and quick outs. That helped.
"We were definitely on a pitch count over there, and it was definitely one of those magical seasons," Shields said. "I had three complete games in a row twice. It's kind of the way it fell. It's just a testament to staying aggressive and trusting your stuff. There were a couple times I was just pinching myself because obviously, as a pitcher, you want to get some complete games, but 11 complete games in one year? Especially in this day and age, where there are closers, setup men, lefty specialists and all the sabermetrics stuff. Yeah, it was a great season."
The changeup, obviously, was working just fine.