Terms of the deal were not announced but NFL Network Insider Ian Rapoport reported the contract is worth $20.4 million.
In another move reported by multiple media outlets, the Lions signed former New England Patriots linebacker Marquis Flowers.
Diggs can play either cornerback or safety and his versatility made him valuable. He was entering the final year of his contract, which pays a base salary of $1.9 million.
A sixth-round pick out of Texas in 2015, Diggs has appeared in 44 games with 19 starts. He became a starter last season, when he started 11 games, making the switch from slot cornerback to strong safety in December when Tavon Wilson suffered a torn biceps. Diggs had a career-high 55 tackles, a sack, three interceptions and nine passes defensed in 2017.
“Quandre has developed into one of our core defensive players and we are excited to come to this agreement that will have him as a Detroit Lion for the next four seasons.” Lions general manager Bob Quinn said on the team’s website. “I also want to thank Quandre and his representatives for their work in making this extension a reality.”
Diggs is expected to start at one safety spot this season along with Glover Quin.
The Lions ranked 27th in the league in pass defense last season.
Flowers, 26, reunites with Matt Patricia, who was the Patriots’ defensive coordinator last season and is now the Lions’ head coach. Flowers played in all 16 games, including two starts, for New England last season, when he had 30 total tackles and 3.5 sacks
The Patriots released Flowers on Saturday, and because he is a vested veteran he did not have to go through waivers.
The Lions need help in their front seven, and Flowers should help them in pass coverage as well as assisting on special teams.