Cameron Smith, the 24-year-old linebacker who started in the Vikings' preseason opener 355 days after successful open-heart surgery, announced his retirement via Instagram on Wednesday evening.

"For the past 18 years, football has been such a tremendous part of my life," Smith wrote. "It has provided countless friendships, incredible memories, and invaluable lessons that will last a lifetime. When I had open heart surgery last year, I grappled a lot with what I had been asking my body to do in order to play this great game. Ultimately, I've decided that I've been asking for it to do too much.

"After careful consideration and thorough discussion with my friends and family, I have made the difficult decision to retire from the NFL. I know this transition isn't going to be easy, but I am excited to tackle this next chapter of my life with the same passion and pursuit that I did football. I am grateful for, and will forever cherish, the many opportunities that I have been given to me through football.

"I truly appreciate the support from all my friends, family, the entire Vikings organization, USC, Athletes First and everyone who has been by my side along the way.

"Thanks again, Cam."

A fifth-round pick from USC in 2019, Smith played in five games as a rookie. He was set to open his second season when the Vikings discovered he had a bicuspid aortic valve birth defect that would have gone undetected if not for COVID-19 testing.

"It probably saved my life," Smith said. "I just look at God and I say, 'Thank you. I appreciate You giving me this sign.'"

Smith's initial COVID-19 test came back presumptive positive. Not definitive enough to trigger protocol for a cardiac workup. But his other test for the COVID-19 antibodies came back positive, meaning he had contracted the virus at some point and would require a closer look at his heart. A closer look that uncovered the defect.

"The antibodies [blood] test was optional, and Cameron took it," said Vikings head athletic trainer Eric Sugarman. "Pretty remarkable that sometimes things happen for a reason."

Smith had surgery Aug. 24, 2020. His first practice was May 24. Last Saturday, he played 18 defensive snaps and six special teams snaps before suffering a concussion and exiting the field for the final time of his career.