"I was fortunate to have been drafted by the Colts ten years ago. I was even more fortunate to spend my entire career here in Indianapolis. The Indianapolis Colts is a special organization with special ownership who fill the organization with special people at every level. I truly believe this is the best organization in all of sports. I am lucky to have been able to call myself a Colt for the past ten years and will consider myself a Colt for the rest of my life.
"I have given much to the game of football, but it has given me so much more. I close the book on the football chapter of my life gifted with memories and moments I wouldn't trade for anything. So thank you, last but far from least, to football."
Castonzo spent his entire NFL career in Indianapolis, starting all 144 of his games played.
While he never made a Pro Bowl, Castonzo provided consistency to the Colts' left tackle spot by rarely missing games. Indianapolis may shift its focus in the first round of April's draft to finding Castonzo's replacement in hopes of a seamless transition.
The Colts could target names like Virginia Tech's Christian Darrisaw or Texas' Samuel Cosmi with the No. 21 overall pick.
Whoever steps into that tackle spot next will have massive shoes to fill.