Ben Simmons' long-awaited debut with the Brooklyn Nets was a major failure. He fouled out with just 4 points and 5 assists, was unaggressive in the offensive end, and failed to make a defensive impact.

Even Kyrie Irving claimed that Simmons' wasn't smart enough and that they need him on the court if they're going to go the distance this season. Simmons, on the other hand, excused himself by stating he was overly excited.

Whatever the case, and even though the season is just getting started, Simmons left a lot to be desired with that performance. That's why Kendrick Perkins believes he doesn't have that killer mentality, and that's never going to change.

NBA News: Kendrick Perkins Puts Ben Simmons On Blast, Claim He's Not That Guy

"We keep acting like Ben Simmons is gonna come back and have some type of All-Star caliber season. And this is the thing, we question a lot of people when it comes down to having that killer instinct, that killer mentality when we talk about guys like LeBron and the late great Kobe Bryant," Perkins started. 

"I realized this: Ben Simmons ain't nothing but a family dog, a good golden retriever," Perkins said. "When a stranger comes ringing the doorbell, instead of him barking and getting aggressive, he get to wagging his tail. And he's not gonna change."

"I look at it like this: Zion Williamson did whatever the hell he wanted. Okay. If Ben Simmons is not gonna be aggressive offensively, what is he known for? He's known for being one of the most versatile defenders in the league. He didn't show that. You also just said he showed up not ready to play. How are you not ready to play on a new team in a new situation, after what you did last year in Philly?" Perkins concluded.

Simmons is one of the greatest pure talents to set foot on an NBA hardwood in the past two decades. But it seems like he'll never live up to those expectations, as he doesn't seem mentally strong enough to get it done.