Biggest issue with him has been health the last 2 years. He had a torn pectoral muscle and I believe and ankle injury causing him to miss most of the last 2 seasons. Prior to that, he was a pretty decent ILB according to reports. When he signed his 4 year deal, here was what was written about him per PFF:
Kirksey has elevated his play in each of his first three seasons and in 2016 he graded as tied for the 22nd best off the ball linebacker with an overall grade of 81.5.
• Kirksey has developed into a dominant force defending the run. In 2016 his run-defense grade of 84.9 ranked fourth among linebackers and his 46 run stops ranked first amongst inside linebackers(A stop is a tackle resulting in an offensive failure).
• In 2016, Kirksey was effective as a pass rusher off blitzes. His pass-rush productivity of 16.0 ranked fifth among inside linebackers with at least 40 pass rush snaps. He produced 16 pressures (two sacks, four hits, ten hurries) on 78 pass rush snaps.