He has experience playing a top-two cornerback role, going against an opponent’s best receivers each week. He has spent the last two years playing the “nickel” (inside) spot. He blitzed 38 times in 2017 and isn’t shy about defending the run. Welcome to the curious case of Aaron Colvin. Colvin, the Jaguars’ fourth-round draft pick in 2014, will be a free agent if the sides can’t agree to a new contract by March 14. Jaguars general manager Dave Caldwell agreed last week that Colvin’s case is odd. “It’s going to be interesting because he has a niche position that there aren’t a lot of comparatives for,” Caldwell said at the NFL Scouting Combine. “A lot of it will be about does he really want to be back and can we pay him?” Is there a gray area for Colvin’s value because there are so few similarities? “I think I know what the market is going to be, but all it takes is one team,” Caldwell said. “You’ve seen it from us in the past — we set our limit and then we have to walk away at some point.” Ideally, the Jaguars would retain Colvin and keep the NFL’s best secondary intact, thus creating one fewer need to address in free agency and the draft. Colvin was present for many lean Jaguars years but was energized by the team’s appearance in the AFC Championship Game.