KANSAS CITY -- James Shields posed for photographers in uniform No. 24 when he checked into Kauffman Stadium for the first time as a Royals pitcher. But that might change, probably should change.

Shields is partial to No. 33, which he'd worn for the past six years with Tampa Bay. But 33 currently belongs to Jeremy Guthrie, and Shields playfully said he's negotiating with his fellow starter for the number. Not that it's part of Guthrie's baseball DNA; he'd never worn 33 in the Majors until he arrived in Kansas City last July, apparently content with five other numbers previously.

Wearing a favorite number, after all, is often a perk of being the No. 1 pitcher on a staff or, as they've called him since Grantland Rice was a cub reporter, "the ace."

Which, in the course of Shields' introduction to a cluster of KC media, he was asked to define. How about it, ace?

"There are a lot of intangibles that go along with that," Shields ventured. "You have to be a leader, you have to compete every day and give your team a chance to win, go deep into games. Throwing a lot of innings and saving the bullpen is huge. Just being able to show a good example."

Shields never seems to be at a loss for words, but Wade Davis, his quieter wing man from Tampa Bay, helped fill out the job description.

"Along with being a really good pitcher, it'd be somebody that can lead an entire pitching staff, not only just starting pitchers but relief pitchers, too," Davis said. "He's usually a little bit smarter, a little more confident and comfortable in any situation -- whether it's postseason, Spring Training, regular season, winning or losing. It's those guys you turn to, you feel comfortable around and guide you in the right direction."

There you have it: What Shields is supposed to do for the Royals next season.

He's had some practice. In the past two seasons for the Rays, Shields was a combined 31-22 with a 3.15 ERA. In 2011, he pitched 11 complete games -- more than 26 Major League teams had that year. In 2008, Shields led the World Series-bound Rays with a 14-8 record, a 3.56 ERA and 33 starts. He's logged over 200 innings in each of the past six seasons. That definitely puts him in "horse" category.

Then there's that leadership around the clubhouse and in the dugout.

"He had a huge impact on me personally and everybody around us," Davis said.

Shields has pitched a one-hitter, struck out 15 in a game and won in a World Series. On Aug. 2, 2009, he held the Royals hitless through seven innings but wound up losing the game, 4-1. That was one of only two losses inflicted upon him by Kansas City, against his seven victories.

Shields is sometimes referred to as "Big Game James" but that nickname was purloined by some of his pals from the Lakers' James Worthy while Shields was still in the Minors. He grew into it, though.

Old school? You bet. After Boston's Coco Crisp angered the Rays with a second-base slide in a 2008 game, Shields drilled Crisp in the hip the next day to ignite a skirmish that got both players a suspension.

But among his teammates, Shields can keep things light.

"He's going to be a big personality in the clubhouse and he's going to make people laugh a lot," Davis said.

The two pitchers are looking forward to their new catcher, Salvador Perez who, as it happened, made his Major League debut in 2011 at Tropicana Field against Tampa Bay. He got his first hit off Davis, picked off two runners and caught five popups.

"We sit in the dugout across the way, and he's got so much emotion, he's into every single pitch," Shields said. "[Luke] Hochevar would strike a guy out and he's fist-pumping. Obviously, he's a talent, but besides that, the passion that this kid has for the game is amazing."

Davis nodded agreement.

"When you have somebody back there getting pumped up, that's the best thing there is," Davis said.

Shields smiled and added: "It doesn't matter how bad you're doing, it makes you feel good. So we're excited to work with him."

Shields, who'll turn 31 in a week, is married to Ryane, a photographer, and they live in Clearwater, Fla., with their two daughters. A favorite off-field pursuit is providing support and assistance to foster children. He's an aspiring chef and he's an author; Shields' 2011 book, "September Nights" was written with MLB.com's Bill Chastain.

The pitcher is from Newhall, Calif., starred at William S. Hart High School and was drafted in the 16th round in 2001 by Tampa Bay. He missed the 2002 season because of shoulder surgery.

Time moves on, and after seven seasons with the Rays under Tropicana Field's dome, Shields comes to Kansas City as the great hope.

"I'm up for any challenge. There's no doubt I'm the type player that likes the challenge," he said.

Shields believes that he and Davis can make a difference.

"It's not just about me or just about Wade or one individual guy, it's about the whole entire team. And the only way to do that is to create good chemistry and good, friendly competition," Shields said. "If I go out there one day and throw eight innings, Wade's going to come in right behind me and try to throw nine. That's the kind of culture that I've always been accustomed to and I want to create here."