The Buckeyes had one of the best defenses in the country in ’16 and ’17 but allowed more points and yards than any stop unit in school history this past season.
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Mattison is veteran assistant coach who left the Baltimore Ravens to coordinate Michigan’s defense for head coach and Kettering native Brady Hoke in 2011.
Considered an elite recruiter, he was retained as defensive line coach when Jim Harbaugh replaced Hoke in 2015.
Mattison’s numerous coaching stops include three years as an assistant for Urban Meyer at Florida from 2005-07.
(Day, who replaced Meyer as head coach of the Buckeyes last week, was a graduate assistant at Florida in 2005.)
Hafley spent the last seven seasons in the NFL, including Chip Kelly’s 2016 49ers staff of which Day was also a member.
Hafley will coach the secondary while Mattison’s position group is to be determined.
Along with hiring Mattison and Hafley, Day announced the promotion of veteran defensive line coach Larry Johnson to associate head coach.
This news comes after the departure of Alex Grinch, who had the title of co-defensive coordinator last season but left last week to become defensive coordinator at Oklahoma.