Former A's and Giants left-hander Barry Zito, a three-time All-Star and the 2002 American League Cy Young Award winner, announced his retirement on Monday.
Zito, 37, made the announcement in an article, titled "What Baseball Taught Me," posted on the Players' Tribune website.
After taking a year off in 2014, Zito returned this year to the organization that drafted him and helped him develop into a star. He spent most of the year pitching for Triple-A Nashville before making three September appearances for the A's.
Zito made his second-to-last start on Sept. 26 against the Giants and former Oakland teammate Tim Hudson, who was part of the A's "Big Three" in the early 2000s with Zito and Mark Mulder.
"I'm retiring today from baseball, but I'll never be too far away from the game that made me who I am," Zito wrote. "I am beyond thankful to be at peace with walking away, thanks in large part to my year of renewal in Nashville with the Sounds.
"My return to Oakland last month was a 'cherry on top' moment in my life that my family and I will never forget. I will no doubt be in the stands on both sides of the Bay in years to come."
Zito will retire with a 165-143 record and 4.04 ERA in 433 appearances. As he mentioned in the announcement, he experienced a number of ups and downs throughout his 15-year career.
After seven outstanding seasons with the A's, Zito signed a seven-year, $126 million deal with the Giants before the 2007 season. Unable to recapture his A's success across the San Francisco Bay, Zito was left off the Giants' postseason roster when they won the 2010 World Series.
Two years later, Zito delivered two key starts for the Giants, including a win over Justin Verlander and the Tigers in Game 1 of the 2012 World Series.
Now that his baseball career is over, Zito wrote that he will become a "rookie" once again -- as a songwriter.
"My baseball career has been a mirror to my life off the field, full of euphoric highs and devastating lows," Zito wrote. "I've been at the top of a rotation and the 25th man on a roster. I've started Game 1 of a World Series in one year and I've been left off of a postseason roster in another. I've been labeled as both drastically underpaid and severely overpaid. I've been praised as a savior and deemed a curse. The thing I take the most pride in, however, is not my career itself, not the Cy Young or even the World Series rings.
"Beyond all of the achievements, the single thing that fulfills me today is the acceptance of myself as a worthy and valuable person, regardless of what my stature or position in the world was on a given day of my career."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.