OAKLAND, Calif. -- Billy Butler came so close to winning it all with Kansas City that it stings to be leaving his only professional team after such a special run, and with some unfinished business.

Then the Oakland Athletics came calling when his old club did not, and Butler is someone who prides himself in loyalty -- in this case to A's general manager Billy Beane's persistence and interest in striking a quick deal.

The versatile Butler finalized a $30 million, three-year contract with the A's on Wednesday. He receives a $5 million signing bonus payable by Dec. 31, a $5 million salary next year and $10 million in each of the final two seasons.

"We gave them a chance," Butler said of the Royals. "It didn't work out. It's unfortunate. I enjoyed every day of the last 10 years, 10 years is a long time, just in life. I enjoyed every minute of it. It dampens it a little bit for me that we got to the top of where we're at and now I'm gone. I'm glad I got to see it through this year. ... It hurts a little bit that I'm not going to get to see the rest of that go through. I'm on to a different chapter, that's the way you have to look at it."

"I've got nothing to be ashamed of. I'm really honored to have been a Royal."

Always looking for a middle-of-the-lineup hitter with pop, Butler provides manager Bob Melvin another player who can contribute at multiple positions.

"We felt there were a number of teams out there looking for bats that might have had him somewhere on their depth charts, and once one or two guys came off the board, there was going to be more intensity in terms of the pursuit," Beane said.

Butler helped the Royals reach the World Series last month after a 29-year playoff drought. In the postseason opener, they rallied late to eliminate Oakland 9-8 in the AL wild-card game. Butler contributed two hits and two RBIs in the 12-inning game.

After losing to the San Francisco Giants in a seven-game World Series, the Royals declined their $12.5 million option on Butler for next season. The 2012 All-Star received a $1 million buyout and became a free agent for the first time in his eight-year major league career.

"Finding right-handed power in the middle of the lineup at this stage is really difficult," Beane said. "It's not very often you get free agents that are in the prime of their career and still have some upside to them."

A steady and productive hitter for most of his career, Butler is coming off a down season. He batted .271 with nine home runs and 66 RBIs in 151 games this year, 108 of those as a DH.

Free agent DH Billy Butler has agreed to a three-year, $30 million deal with the A's. AP Photo/Charlie Riedel

Before that, he played at least 158 games in each of the five previous years, including all 162 in 2013.

"I take pride in getting back to where I was. I'm 28 years old, I'm not on the other side of my career," he said. "It's just a year a lot of things didn't go right for me mentally or approach-wise."

Butler's best season was 2012, when he batted .313 with 29 homers and 107 RBIs. He made the All-Star team that year, when the game was played in Kansas City.

He dropped off to 15 homers and 82 RBIs in 2013, then struggled at the plate this year. As the Royals chased a playoff berth during the stretch run, he was regularly held out by manager Ned Yost in late September.

Once the Royals qualified for the playoffs, though, Butler returned to the lineup.

In his first postseason, he hit .262 (11 for 42) with eight RBIs, three doubles and a stolen base in 13 games as Kansas City won its first pennant since 1985.

Royals general manager Dayton Moore said Kansas City is trying to spread its financial resources "to build a team that was a little better balanced going forward." Butler said he kept in touch with the Royals about a "strong offer on the table."

"We'll miss him, no doubt," Moore said.

Beane has often been aggressive in the trade market in past Decembers but doesn't consider that a focus this offseason.

"We're not going to be so aggressive in trading some of our younger players," he said. "Now, I think we need to consider some focus on younger players who are with us already or consider bringing some in. Some players we're not going to trade regardless."

Also Wednesday, agent Marc Kligman posted on Twitter that client Pat Venditte signed a minor league deal with Oakland that includes an invitation to big league spring training for the switch pitcher.