BALTIMORE—Eleven years after he was drafted by the Tampa Bay Rays in the 44^th round, a 33-year-old rookie is preparing for his major league debut.

When Mickey Jannis takes the mound for the Orioles, he’ll be the third-oldest rookie in team history. Only Jay Heard, who was 34 years and 97 days on April 24, 1954, and Koji Uehara, who was 34 years and five days on April 8, 2009, were older.

It’s not just Jannis’ age that sets him apart. It’s his specialty, the knuckleball, and the hope that he can pitch multiple innings because his primary pitch isn’t as tough on the arm.

“I don’t think I could pitch it into words what it means,” Jannis said about being called up. He found out in a phone call from Norfolk manager Gary Kendall, who told him the Orioles had selected his contract.

“You’re headed to the major leagues, congratulations,” Kendall told him. “It’s a major accomplishment. Best of luck to you up there. Do what you’ve got to do to stay.”

Jannis told his wife, Emily, the rest of his family and a couple of friends. “They were all surprised. A couple of my buddies didn’t believe me. They were like, ‘no way, no way.’ They thought I was messing with them, but I was like, ‘yeah, it’s happening.’ It’s crazy.”

Drafted as a conventional pitcher, Jannis reinvented himself as a knuckleballer during a three-year stint in Independent ball. He pitched for the New York Mets organization and appeared in four Triple-A games before signing with the Orioles before last season.

At Norfolk, Jannis was 0-1 with a 2.92 ERA in seven games.

“Deep down, I always believed I could pitch in the major leagues,” he said. “That’s why I never gave it up. I told my wife, as long as I feel I have a chance to pitch in the major leagues, I want to pursue this dream. She was all for it, backed me up. My parents backed me up.”

Jannis didn’t pitch in Tuesday night’s game, but got to savor his first day in a big league uniform.

“I was just trying to take it slow and take it all in, look around and try to enjoy the moment,” he said. “It’s really special. It’s something you can’t really put into words.”

Manager Brandon Hyde, who caught in the minor leagues, doesn’t know much about Jannis.

“I have zero experience with knuckleballers,” he said. “I’ve seen R.A. Dickey across the way.”

Jannis throws the knuckleball 80-to-90 percent of the time with an occasional fastball and slider. Wednesday night’s starting catcher Austin Wynns caught him in spring training but not while they were at Norfolk. Pedro Severino wanted the experience of catching him, so Jannis threw to him before Tuesday night’s game.

Hyde laughed when he asked if was confident his catchers could deal with the knuckler. “Sort of,” he said.

There aren’t any other knuckleballers in the majors, and the Orioles haven’t had one since Daniel Boone pitched in four games for them in 1990.

“Deep down, I wanted to give myself that opportunity, knowing that I was one of the few left,” Jannis said. “Especially in this day and age where everything’s about velocity, spin rates and things like that. I’m taking spin off the ball. It got me here.

“It’s not just about being here. It’s about staying here. Until I get out there and pitch and really get on the mound, I think that’s when it will really sink in.”

Lots of players experiment with the knuckleball, but other than the occasional position player called on to pitch, few actually throw one. Jannis is the Orioles’ knuckleball guru.

“Everybody usually comes up to me and asks me how I throw it,” he said. “Some guys want to throw me their knuckleball. They mix in one or two good ones. It’s pretty cool to have everybody come up to me and ask: ‘How do you throw a knuckleball so awesome? I think people don’t see [it] very often. It’s a cool thing to keep [in] baseball.”