TEMPE, Ariz. -- Kevin Minter will have to start looking over his shoulder.

When the Arizona Cardinals signed free-agent inside linebacker Donald Butler on Wednesday, they added instant competition for Minter’s job. It’s still Minter’s to lose as the Cardinals report to training camp Thursday, but Butler adds a dynamic that wasn’t there in 2015: Someone who could take Minter’s gig.

Unless Minter has an awful training camp and Butler is a sponge with a Mensa-level IQ, it’s unlikely Butler will supplant Minter this season. But with the 25-year-old Minter entering the final season of his rookie contract, Butler could be playing for a starting job next season. At 27, Butler is entering his football prime. He signed a seven-year contract worth $51.8 million in 2014 but was released by the Chargers in March in favor of a younger batch of inside linebackers.

After starting all but two games he played in from 2011 to 2014, Butler started just nine last season. Minter started all 16 in 2015, his first season as a starting inside linebacker.

Butler comes to Arizona to compete for just one inside linebacker job. The other in defensive coordinator James Bettcher’s 3-4 scheme belongs to "dollar" linebacker Deone Bucannon. But if Butler were to supplant Minter, he’d be replacing the Cardinals’ second-leading tackler last season. That, coupled with the amount of time it would take Butler to learn the Cardinals’ offense as well as Minter in order to direct it in the huddle, makes it unlikely Butler will start in 2016.

It is plausible that he makes the roster as Minter’s backup, a role that would have been filled by either Alani Fua or Gabe Martin. Both were undrafted in 2015 and both lack the experience Butler provides. And it’s also possible that Butler could be the in the cards for 2017 should the Cardinals not re-sign or extend Minter.