An Under-the-Radar Addition: Heading into free agency, a number of outlets suggested Derrick Shelby is one of the most underrated options available. He's someone who had to play behind Cameron Wake, who prevented Shelby from earning a starting job before his last contract expired. When Shelby got opportunities to play, though, he fared extremely well last year. In the final five games of 2015, the 6-foot-2, 280-pounder registered two sacks, three QB hits, three pass breakups, 10 QB hurries and 10 stops. He also earned a pick six on Dec. 5 against Baltimore and Matt Schaub, who also signed with Atlanta this week.

Strong Hands: Scouts and other talent evaluators agree that Shelby's hand technique is one of his greatest strengths. This likely caught the attention of Dan Quinn, who places a big emphasis on handwork.

A Stout Run-Stopper: Based on last year's numbers, Shelby is one of the best run-stoppers among NFL 4-3 defensive ends. In that group, only eight posted higher run stop percentages, and only three compiled more stops against the rush.

Entering His Prime: Shelby hit free agency at a good time for the Falcons. As someone who turned 27 last week, the University of Utah alum is fresh enough to give Atlanta his best years physically. Signed through 2019 at a relatively modest cost, Shelby and Vic Beasley, Jr. could do a lot of damage together in the coming seasons.

Valuable on All Three Downs: While Shelby is at his best when defending the run, he's grown into a viable pass-rusher, as well. In the last five games of 2015, when he was starting in place of the injured Wake, Shelby generated 16 QB pressures from the left side—more than all but eight other 4-3 defensive ends in the league.