CHICAGO -- Starlin Castro recalled his Major League debut, which began with a home run in his first at-bat at the age of 20, thanked Cubs fans for their support, talked about Mr. October, and called the trade to the Yankees "bittersweet" in a first-person essay posted Wednesday on "The Players' Tribune" website.
Castro, 25, played from 2010-15 with the Cubs and was a three-time All-Star at shortstop. On Dec. 8, he was dealt to the Yankees for pitcher Adam Warren and a player to be named.
"My career started in the best way possible: a home run," Castro said of his big league debut May 7, 2010, in Cincinnati, when he drove in six runs. "But not every at-bat can be a home run. ... Baseball, like anything else, is full of ups and downs -- and my five years in Chicago had its share of both."
Castro said Cubs fans were always good to him and that he could not thank them enough.
"When I got to Chicago, I was just a kid, trying to figure things out at a new job in a new city," he said. "When you're new, you want to be approved of, and you want to belong. Those first big cheers I got at Wrigley are something that I will never forget. They helped me feel like I was doing something right -- and they helped me feel like I was home."
He noted a lot of his favorite memories involve becoming a father, and recalled fishing on Lake Michigan with his son, Starlin Jr., and playing catch at a park. Castro also thanked the Cubs organization for "everything."
"You gave me an opportunity, you believed in me and you were always honest with me," he said. "You didn't just help me grow as a player; you helped me become an adult."
He made sure to thank former teammate Alfonso Soriano, who mentored Castro when he was called up. Soriano, who turned 40 on Thursday, is a godfather to Castro's son.

Castro also acknowledged that he struggled when he was replaced at shortstop by rookie Addison Russell in August, but noted that he did not want to be a negative influence on the team. When given the opportunity to win the second-base job, Castro took it seriously.
"I tried to treat it like a new beginning," he said.
Castro rebounded, batting .426 in September to help the Cubs reach the postseason for the first time since 2008.
"Out of all my accomplishments as a Cub, that is the one I hope people talk about when they look back on my career: That in a situation where some players would have checked out, I kept my head up and worked even harder," he said. "I didn't just say, 'I want to help the team win.' I actually helped the team win."
He says his goal now is to help the Yankees win, adding that he's at a stage in his career "where I just want to win. Period."
Carlos Beltran was among the players to reach out to Castro and welcome him to the Yankees. His favorite "welcome to New York" moment came when Yankees legend Reggie Jackson called to offer advice and encouragement.
"I think I smiled for the rest of the day after we got off the phone," Castro said.
Last year was the first time in Castro's career that the Cubs posted a winning record and reached the postseason. He's eager to play more baseball in October.
"To my new city, New York, I can promise you this: You are acquiring a player who just got to experience a pennant race for the first time -- and loved it," Castro said. "And to my old city, Chicago, I want to thank you for such an amazing experience. I'll always hold Chicago close to my heart. And hey -- maybe I'll still visit sometime. How's October?"