CHICAGO -- Rich Hill's career is climbing fast. The left-hander, who started this season at Double-A West Tenn, was called up to the Chicago Cubs on Wednesday.

Hill, 24, will be assigned to the bullpen for now and be used in long relief. Lefty John Koronka was optioned to Triple-A Iowa to make room on the 25-man roster. Hill will wear No. 53.

The Cubs will go with a four-man rotation for now -- Greg Maddux, Carlos Zambrano, Glendon Rusch and Sergio Mitre -- because they don't need a fifth starter until next week in Milwaukee. Hill will not necessarily be slotted into that fifth spot, although he had been starting at West Tenn and at Iowa this year.

"He'll go to the pen first," Cubs manager Dusty Baker said. "I think it's better to bring a young man in in long relief in the beginning."

Right-hander Jerome Williams, acquired from San Francisco in the LaTroy Hawkins trade, was to start Wednesday for Iowa, and could be a candidate for that fifth spot.

"By the time we get to Milwaukee, then we might have another plan," Baker said.

In 76 career Minor League games, Hill was 13-19 with a 4.06 ERA and 416 strikeouts. He's held opposing batters to a .212 average. In Double-A, he was 4-3 with a 3.28 ERA in 10 starts, and went 1-1 with a 4.34 ERA at Iowa.

In Triple-A, Hill struck out 29 over 18 2/3 innings and held opponents to a .176 average. A fourth-round pick in 2002, Hill said he didn't expect to get called up but was prepared.

"It's all been a course of good mental attitude, and a positive attitude through the whole thing," he said. "It's not expecting anything but being prepared. I prepared myself for each situation as I've come up each year."

This offseason, he not only worked out to improve his velocity -- he's throwing 90-91 mph consistently -- but also wanted to help himself with the mental part of the game.

"I did a lot of work this offseason mentally, working on things such as positive attitude and building little phrases," he said. "'Act as if.' Act as if you're a big leaguer. The way you carry yourself and the way you handle yourself -- it changed the way I approached the game coming into this Spring Training."

Hill was added to the Cubs spring roster for their final exhibition games in Las Vegas, and he enjoyed that experience. Two coaches gave him the book "Thinking Body, Dancing Mind," which he said clicked.

"It deals with every aspect of the game," Hill said. "It pretty much comes down to all the pressure you put on is put on by yourself. You can't control the outside factors. Where it comes from is from yourself."

He'll be thrown into a pressure-packed park this weekend. Hill's first road trip will be at Yankee Stadium, where the Cubs will play an Interleague Series.

"First, to get told you're going to the big leagues, and you're stunned for about 15 minutes and then it wore off," Hill said. "You prepare for it and take it for what it is."

His best pitch is a curveball, which he uses as his out pitch and isn't afraid to throw in any count.

"I just describe myself as someone who goes after hitters and doesn't give in," he said.

"He can pitch because he's not afraid to throw the ball," Cubs pitcher Carlos Zambrano said. "If he can do it in the Minor Leagues, why can't he do it in the big leagues?"

Frequent flyer: Koronka, who was 1-2 with a 7.63 ERA in three starts, will rejoin the Iowa Cubs a better pitcher.

"You have to control your emotions out there, and I was just trying to do too much -- that was the biggest thing," said Koronka, who was optioned to Iowa to make room for Hill.

"It was a good experience," Koronka said. "When I go back down there, I should be better than I was before. This is nothing now -- I've been up in the big leagues and I've gotten those hitters out, and now I have to get these guys out. If another spot opens up, I'll be ready."

Welcome to the show: Mark Pawelek, the Cubs' No. 1 draft pick, threw in the bullpen before Wednesday's game in his first trip to Wrigley Field.

"It was the coolest feeling I've ever felt in my life," the 18-year-old left-hander from Springville, Utah, said about pitching at Wrigley. "Growing up as a kid and watching the Cubs play, this being one of the greatest fields in baseball, it was awesome to go out there and throw on it."

Pawelek will report to Mesa, Ariz., in a couple weeks to join the Cubs rookie team there and begin workouts.

"I want to play," he said. "That's why I signed so quickly because I want to start my professional career as soon as I can. it can take a few years for me to get up here. It's the Cubs decision to call me up."

He is postponing his two-year Mormon mission to begin his baseball career.

"The reason I did that is this opportunity I can't pass up," he said. "The Cubs and the organization, I've followed since I was little. It's really cool."

He was wide-eyed meeting Cubs like Michael Barrett, Carlos Zambrano and Mike Remlinger.

"I've got to get used to this -- meeting guys I've seen on TV," Pawelek said after shaking Barrett's hand.

Baker remembers the first time he worked out with the big league team after signing.

"[The fans] didn't know who I was because I didn't have a number on the back, so my name was 'No Number,'" Baker said. "'Hey, No Number, what's your name?' I told them, and they still didn't know."

Day after: Sergio Mitre fielded calls from friends and family after Tuesday's impressive complete-game shutout over the Florida Marlins. The right-hander, called up May 24, gave up five hits and did not walk a batter, throwing 99 pitches (73 for strikes).

Mitre is hoping he can settle in with the Cubs, and doesn't want to shuttle back and forth between the big league team and the Minors any more.

"I got tired of doing that," he said. "It'd be nice to settle down for somewhere for more than two months. I've been up here, I've seen what it's all about. It's about time to show what I can do."

And games like Tuesday's, which was his first big-league complete game and shutout, certainly help.

"It helps my confidence," Mitre said. "It shows everybody what I'm capable of doing. Like I've always said, it's a matter of being consistent."

He's also made some adjustments. Mitre has shortened his arm slot, something he started working on last year with Minor League pitching coaches Rick Kranitz and Lester Strode.

"They're making sure I stay on top of the ball," Mitre said. "The arm slot was a little too long and kind of pulling out and dragging. It's just shortening up the arm slot."

Mitre's next start will be Sunday at Yankee Stadium.

"I'm not worried about Sergio," Baker said. "He's a mature young man, plus we have guys here who can help him out."

New York, New York: Todd Walker will be asked to talk to some of the Cubs players who have never been to Yankee Stadium about the historic ballpark and all of its ghosts.

"You look at it in reverence but not in awe," Baker said. "Look at the monuments but don't adhere to it too much."

Minor matters: Raul Valdez gave up four runs on 10 hits over six innings in Iowa's 6-5 victory over New Orleans on Tuesday. Ben Grieve hit a solo homer and Ronny Cedeno drove in the game-winning run with a double in the eighth. ... Renyel Pinto threw six scoreless innings in West Tenn's 2-1 win over Huntsville. He struck out six. Matt Murton and Casey Kopitzke each went 2-for-4. Ryan Theriot hit a game-winning solo homer in the eighth. ... Sean Marshall gave up three runs on six hits over six innings while striking out 11 in Daytona's 6-5 loss to St. Lucie. ... Ryan Harvey was 3-for-5 with a pair of doubles, a homer and three RBIs in Peoria's 6-1 win over Quad Cities. Chris Shaver gave up one run on five hits over seven innings. Eric Patterson hit a solo homer, and was 3-for-5.

On deck: The Cubs have Thursday off and then travel to Yankee Stadium for a three-game Interleague Series against the Yankees. Carlos Zambrano will start Friday against Carl Pavano. Glendon Rusch will pitch on Saturday for the Cubs, and Mitre on Sunday.

Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.