"I get an opportunity to retire as a Steeler, which is very important to me," Clark said on the ESPN set at the NFL scouting combine in Indianapolis. "To be able to play with some of the greats in Troy Polamalu, James Harrison, [James] Farrior, the opportunity to play with Sean Taylor and to do things I never dreamed of ... when I signed at LSU, I was just there to get an education. To have an opportunity to win a Super Bowl, play in another and play in a Pro Bowl, it's been amazing."
Clark, 35, played 13 seasons in the NFL and started at free safety for the Steelers from 2006 to 2013. He made the New York Giants as an undrafted rookie in 2002 and spent two stints in Washington, playing his final NFL season in 2014 with the Redskins.
Clark rose to prominence while in Pittsburgh, serving as a perfect complement to Polamalu, a perennial Pro Bowl safety. The two became close friends off the field and meshed well on it, anchoring the back end of a defense that led the Steelers to a sixth Super Bowl title in 2008.
A life-threatening illness nearly derailed Clark's career in 2007.
Clark became seriously ill during an October game in Denver when the high altitude triggered a dangerous reaction with his sickle-cell trait.
A deprivation of oxygen to major organs led to Clark losing more than 30 pounds as well as the removal of his gall bladder and spleen. He missed the rest of the season but returned as the Steelers' free safety in 2008. Clark's teammates voted him the Ed Block Courage Award winner, which is given to a player who has overcome significant adversity.
Clark helped preserve the Steelers' 23-14 win over the Baltimore Ravens in the 2008 AFC Championship Game with the most famous hit of his career.
He drilled Willis McGahee after the Ravens running back had caught a pass over the middle of the field, and the ferocity of the hit knocked out both players. It also caused a fumble that the Steelers recovered with just under four minutes left in the game and ended any chances of a Ravens rally.
Clark played in another Super Bowl in 2010 with the Steelers and made the Pro Bowl in 2011.
He served as a Steelers captain in 2013 and finished his career with more than 900 tackles and 16 interceptions.
Clark said he will continue to serve on the NFL Players Association executive committee and will join ESPN's stable of analysts after working for the network part time.
When asked to sum up his career, Clark said, "Unexpected for most, not for me, and just non-deserving of what I was able to get."