The Lions are hiring Eagles defensive backs coach Cory Undlin as their new defensive coordinator, as Field Yates of ESPN.com tweets. Undlin and Lions head coach Matt Patricia began their NFL careers together as coaching assistants with the Patriots in 2004 and they’re teaming up more than 15 years later. 
Undlin takes over for Paul Pasqualoni, who stepped down/retired at the end of the 2019 season. He comes with ample NFL experience, including stops with the Browns and Broncos, in addition to the aforementioned Pats and Eagles stints. The Eagles’ secondary has not performed well in recent years, but many feel that Undlin was stuck with some iffy personnel.
Even though Undlin is taking over as DC in Detroit, he won’t necessarily call the plays. Patricia quietly took that responsibility away from Pasqualoni last year and he may opt to ease Undlin into that responsibility.
Undlin’s departure leaves yet another vacancy on the Eagles’ coaching staff. They’ll have to find a new DB coach, offensive coordinator, and wide receivers coach after firing Mike Groh and Carson Walch last week.
I find it funny the most deserving coach to be fired this season from the Eagles staff leaves on his own accord for a promotion. Say what you want about the talent he was given, but outside of maybe Maddox, not one player in that defensive backfield improved under his tutelage. In fact, you could make the argument some players regressed. Their technique was absolutely atrocious all season long and that falls squarely on the coach and what he’s teaching. Good riddance, and good luck Detroit. You’re going to need it. Get used to seeing opposing teams take 40+ yard bombs to the house while the nearest DB is trailing 5 yards behind him.
Could it be your just a bit upset that he recognized he was on a sinking ship and decided a life raft was more appealing?
It was a promotion. How is that a life raft? Do you routinely turn down promotions?
Sad to say but I agree with lemon lots of problems to fix.