Former Philadelphia Phillies first baseman Ryan Howard has officially announced his retirement from Major League Baseball. Howard has not played since the 2016 season.

The 38-year-old made the announcement on the Player's Tribune, in a letter titled "Thank you, Philly."

"I'm officially announcing my retirement from the game of baseball. It's almost like I blinked, you know? It's almost like I blinked — and suddenly, September 2004 ... it became September 2018," Howard said.

In the letter, Howard reminisces on some of his favorite memories from his playing career, including his first home run at Shea Stadium in 2004, his Home Run Derby victory in 2006 and his World Series championship run with the Phillies in 2008.

A three-time All-Star, Howard led the National League in home runs twice and also led the league in RBI three times. He was voted the National League's Rookie of the Year in 2005, after playing in just 88 games, and its Most Valuable Player in 2006. Howard finished in the top-10 in MVP voting for five straight seasons, from 2007 through 2011.

Howard ended his letter by thanking his family, friends, and the fans.

"Thank you to the crazy game that I'll miss, and the crazy city that I love. And thank you, from the bottom of my heart, to the most passionate group of fans in the world. Y'all took a chance on this big, quiet kid from St. Louis -- and for that I'll always be grateful."

Howard played all 1,572 games of his big league career in a Phillies uniform, and he finishes his career with 382 home runs and 1,194 RBI.