Updated

Iowa defensive coordinator Norm Parker said Sunday that he's retiring after 13 seasons with the Hawkeyes.

Parker, 70, said in a statement released by the school that he's stepping down following Iowa's matchup with Oklahoma in the Insight Bowl on Dec. 30.

The Hawkeyes have not yet said who will replace Parker, whose retirement will create the biggest opening coach Kirk Ferentz has had to fill in his 13 seasons at Iowa.

"I would like to personally thank (athletic director) Gary Barta, Kirk Ferentz, the coaches, and players at Iowa, along with the fantastic fans," Parker said. "It has been a great time, one that myself and my entire family greatly appreciate.

"After 48 years of doing something I love, it is time to enjoy some time with the grandkids."

Parker's style was never flashy. The Hawkeyes rarely deviated from a traditional 4-3 style of play, didn't blitz much and became known as a "bend but don't break" defense under his watch.

More often than not, Iowa didn't break.

Iowa ranked in the top 10 nationally in scoring defense in 2008, 2009 and 2010 under Parker, who was recently named the Assistant Coach of the Year by the American Football Coaches Association.

But Parker has battled health issues. He had his foot amputated in the fall of 2010 because of diabetes and spent most of the season in rehabilitation and away from the team.

Parker returned for 2011, but the Hawkeyes defense struggled with injuries and inexperience. Iowa ranks 42nd nationally with 23.3 points per game heading into their matchup with the high-scoring Sooners.

Parker began his college coaching career in 1968 and also made stops at Wake Forest, Minnesota, Illinois, East Carolina, Michigan State and Vanderbilt.

"Norm's contributions to our team the past 13 years are deeply appreciated, as he has had a tremendous impact on our program," Ferentz said. "As I have said publicly on many occasions, Norm is a superb defensive coach and has served as a strong role model and mentor for all of our players and our entire staff."