Getty Images

Las Vegas Raiders senior defensive assistant Rob Ryan has seen a lot of players since beginning his football coaching career in 1987, but he says one stands alone as the best of the best. Ryan, entering his third year of his second stint with the Raiders, says defensive end Maxx Crosby gets the title.

"When you talk about Maxx Crosby, you're talking about the best defensive player in the league. Probably in the history that I've ever seen. Now, I've only been around it 30 years, but I mean he's that good," Ryan said, via NBC Sports

Ryan, who got his first coaching job in the NFL in 1994, says what makes Crosby great is not just his talents on the field, but his leadership off it as well. 

"Maxx makes everybody tougher. Maxx makes everybody better. Maxx makes everybody get tattoos. He's just a badass," Ryan said.

During his NFL career, Ryan has coached for the Arizona Cardinals, New England Patriots, Cleveland Browns, Dallas Cowboys, New Orleans Saints, Buffalo Bills, Washington, Baltimore Ravens and Raiders. He has certainly seen his fair share of Pro Bowl-level defensive players, including some Hall of Famers.

He has two Super Bowl rings, both with the Patriots, where he saw players like Ty Law and Richard Seymour both enshrined in Canton. Also during his time in New England, he served as the linebackers coach, working with two Patriots greats, Willie McGinest and Tedy Bruschi. As defensive coordinator of the Raiders, he coached Hall of Famers Warren Sapp and Charles Woodson and in the same role with the Cowboys he had DeMarcus Ware on the roster.

Ryan has seen many greats up close, but for him Crosby is No. 1.

Last season, Crosby had career highs in combined tackles (90) and sacks (14.5). In his 83 career games, the 26-year-old has 321 combined tackles and 52 sacks. 

While there is no doubt the three-time Pro Bowler is a top defensive player, the competition for greatest on that side of the football is not an easy one.