OAKLAND, Calif. — No hard feelings about leaving San Francisco for Santiago Casilla. He is focused on his second stint with Oakland, the place the hard-throwing reliever received his big league start.

"There is a big part of my heart with the Athletics because they believed in me in the first place when they signed me and they believed in me again when they re-signed me," he said Friday. "They taught discipline, they taught me how to play the game of baseball. There are so many things I have to thank the A's for getting my start in the major leagues."

Casilla is crossing the bay once again, re-joining the A's with an $11 million, two-year contract after seven seasons with the Giants.

While the right-hander lost his job as closer in mid-September last season for the Giants' struggling bullpen, he provides A's manager Bob Melvin with some options of when to use him. Casilla could be called upon to help handle ninth-inning duties along with regular closer Sean Doolittle, while Ryan Dull also could be in the mix.

"To be able to sign an experienced late-inning reliever who has performed in multiple World Series games makes our bullpen deeper and obviously better," Melvin said by text message. "Great sign for us."

Casilla gets a $1 million signing bonus, payable within 15 days of the contract's approval by the commissioner's office, and salaries of $4.5 million this year and $5.5 million in 2018.

He can earn $1.5 million annually in performance bonuses based on games finished: $250,000 each for 35, 40, 45 and 50, and $500,000 for 55.

Casilla has spent his entire big league career with the Bay Area teams; his initial six seasons were with Oakland.

He went 2-5 with a 3.57 ERA and 31 saves last season after posting a 4-2 mark record with a 2.79 ERA and a career-best 38 saves in 2015. Yet Casilla blew an NL-high nine saves and manager Bruce Bochy didn't call on him in the ninth inning in Game 4 of the NL Division Series against the Cubs last fall. Five San Francisco relievers squandered a three-run lead by surrendering four runs as eventual champion Chicago celebrated a 6-5 win at AT&T Park.

"That is in the past for me now," said Casilla, who also drew interest from the Brewers this off-season but not the Giants.

When Casilla first came to the A's in 2004, he went by the name of a friend — Jairo Garcia — then later shared in a lengthy interview in Spanish with The Associated Press his deep regrets over something he considered an act of desperation. At the time it seemed like the only way to achieve his dream of pitching in the major leagues. It wasn't even his idea, though Casilla hasn't said who suggested it.

The A's didn't know the hard-throwing pitcher they signed in January 2000 wasn't Jairo Garcia. Not until he finally decided to tell the team through his agent in 2005.

When he returned to the team in 2006 as Casilla, many wondered about the A's new pitching prospect. But to his teammates, he was always Willie — his nickname since childhood.

He has long since moved on from that, and now will begin another new chapter in his career that already included three World Series rings, in 2010, '12 and '14 with the Giants.

"I'm very happy with this new opportunity. There's an old saying that it's always good to return home," Casilla said.

Left-hander Ross Detwiler and outfielder Alejandro De Aza agreed to minor league contracts with invitations to big league spring training. Outfielder Brett Eibner was designated for assignment to clear roster room for Casilla.

A's general manager David Forst wasn't deterred by the way Casilla finished 2016.

"As we got through the off-season, we felt he was being overlooked a little big given some of the narrative surrounding his departure with the Giants," Forst said. "It seems like a few blown saves toward the end of the year marred what was otherwise a fantastic season for him. ... This felt like a really good opportunity to bring an accomplished pitcher into our bullpen. He's willing to do an ything."