-- FOXBOROUGH, Mass. -- New England Patriots defensive end Rob Ninkovich, who has been absent from training camp for what coach Bill Belichick described as personal reasons, announced his NFL retirement Sunday afternoon.
Ninkovich, 33, has been considering retirement in recent seasons. He entered the NFL as a fifth-round draft choice of the New Orleans Saints in 2006. A Purdue alum, Ninkovich didn't see his NFL career take off until he joined the Patriots as a free agent on Aug. 2, 2009.
He played in 123 regular-season games (101 starts) in New England from 2009 to 2016 and appeared in 17 playoff games (16 starts). He was a team captain in 2013 and 2015 and part of two Super Bowl championship teams.
Ninkovich was credited with 423 tackles and 46 sacks with the Patriots, as his steadiness and ability to set the edge in the running game was particularly valuable to the club. Wearing No. 50, he reminded some of former Patriots linebacker Mike Vrabel, who was a key contributor on three Super Bowl-winning teams.
Ninkovich played in 44.3 percent of the defensive snaps in 2016, which was lower than his norm, in part because he served a four-game suspension to open the season after a positive test for a banned substance he said was from an over-the-counter supplement.
But by the end of the year, in the team's most critical games, his playing time had spiked.
This year, Ninkovich projected as a valuable contributor opposite third-year player Trey Flowers, who led the Patriots with seven sacks in 2016. Four-year veteran Kony Ealy, acquired in a trade from the Carolina Panthers, is next on the depth chart, followed by third-year player Geneo Grissom and rookies Derek Rivers and Deatrich Wise Jr.