April 19 (UPI) -- Veteran quarterback Alex Smith, who spent 16 seasons in the NFL and battled severe leg injuries to become 2020 Comeback Player of the Year, announced his retirement Monday on Instagram.
Smith, 36, spent his final three seasons with the Washington Football Team. He became a free agent in March.
Smith entered the league as the No. 1 overall pick in the 2005 NFL Draft. He spent his first eight seasons with the San Francisco 49ers. He played for the Kansas City Chiefs from 2013 through 2017 and was traded to Washington in 2018.
"I was a skinny, no-name recruit who wasn't suppose to play in college, let alone go to New York as a Heisman finalist, or be the first one to have his name called on draft night," Smith said in a video he posted to Instagram.
"Then, on a routine play, I almost lost everything. But football wouldn't let me give up, because, no, this isn't just a game."
Smith sustained a multiple fractures in his right leg in his first season with Washington. The injuries and life-threatening infections required 17 surgeries. He missed six games in 2018 and the entire 2019 season, but returned to the field Oct. 11.
Smith went on to post a 5-1 record and threw six touchdown passes in eight appearances last season.
The three-time Pro Bowl selection was named Comeback Player of the Year in February.
"I want to say thank you for believing in me and thank you for helping me believe in myself and in the impossible," Smith said. "Because even though I've got plenty of snaps left in me, after 16 years of giving this game everything I've got, I can't wait to see what else is possible.
"But first, I'm going to take a little time to enjoy a few of those walks with my wife. My kids have no idea what's coming for them in the backyard."
Smith posted a 99-67-1 record as a starter over his 16 seasons. His career interception percentage (2.1%) ranks No. 9 on the all-time list. He ranks No. 3 and No. 6, respectively, in passing yards for the Kansas City Chiefs and San Francisco 49ers.