Adding a myriad of ex-New England Patriots players and trying to replicate the so-called "Patriot Way" in the Motor City hugely backfired for Quinn, and now the next regime will have to clean up the mess.
A complete overhaul is necessary, and building through the draft will be essential.
Here are the three positions that Quinn's replacement should be targeting in the 2021 NFL Draft.
For all three years of Matt Patricia's failed tenure in Detroit, the defense was the team's Achilles' heel.
And since 2018 (Patricia's first year on the job), arguably the weakest position group on that side of the ball has been linebacker.
Outside of some decent production from Jamie Collins and Reggie Ragland, the group has been an underperforming bunch in 2020, too.
Quinn's 2019 second-round pick Jahlani Tavai has been one of the worst linebackers in the entire league this year, according to Pro Football Focus, and is quickly growing into a draft bust.
It didn't make sense then, and it definitely doesn't make sense now why Quinn reached for a player that was considered a mid-round pick by every other NFL franchise.
The linebackers room also features another draft bust in the form of Jarrad Davis.
Davis was taken by Quinn in the first round (No. 21 overall) of the 2017 NFL Draft, and hasn't come close to living up to the bill of a player drafted that high.
The fourth-year pro is set to be a free agent this offseason, and the Lions are sure to part ways with him.
The only full-time linebackers left on the depth chart are Christian Jones and Jalen Reeves-Maybin, and neither player elicits much excitement. Both players are better suited as reserves.
It leaves Jason Cabinda as the only other player remaining on the roster that's capable of playing the position, and remember, he currently lines up at fullback for the organization.
His linebacking skills, as you probably can surmise, leave a lot to be desired.
Additionally, he, along with Davis, Maybin and Ragland, will be free agents at season's end.
The next regime needs to badly overhaul this position, and should strongly consider doing so via next year's draft.
Kenny Golladay, Marvin Jones Jr., Danny Amendola, Marvin Hall and Jamal Agnew all have contracts that are set to expire at the end of this season. And at this point, there's no guarantee that any of them are brought back.
Additionally, Quintez Cephus, who the previous regime, led by Quinn, took in the fifth round of the 2020 NFL Draft, hasn't developed enough to say that he warrants a bigger role next season.
It leads to a potentially huge void at receiver going into 2021 and one that the next general manager should address in the draft.
Boy, do Detroit's cornerbacks struggle at accomplishing their most important task: Stopping opponents' receivers.
They've collectively been burnt in man coverage all season long, and haven't made many strides, if any at all, since the start of the season.
This includes rookie corner Jeff Okudah, who was taken No. 3 overall in this past April's draft.
Sure, he's a more-than-satisfactory tackler in the open field, but his coverage skills -- which is what the Lions selected him for -- have not been up to par.
He's frequently been beaten when left one-on-one with speedy receivers such as the Carolina Panthers' DJ Moore in Week 11, and it's led to him being graded by PFF as one of the worst cornerbacks in the league for the season as a whole.
Meanwhile, veterans Justin Coleman and Desmond Trufant have only played in six games each due to injury, and Trufant was just placed on injured reserve Thursday with a hamstring ailment.
The only bright spot among the cornerbacks has been second-year defensive back Amani Oruwariye. Yet, he's even had his rough outings, especially in Week 12 against the Houston Texans when he was left one-on-one with Houston speedster Will Fuller.
Beside for Oruwariye, there's no one the Lions can truly rely upon at the cornerback position going into next year.
It's an indictment on the "Quinntricia" era, with Quinn having burnt an aforementioned top-three pick on Okudah. And it's a harsh reality that the new regime will have to deal with and likely will address via the draft next April.
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