Ben Simmons ranks No. 1 on ESPN's Big Board for the 2016 NBA Draft.

"Anyone that doesn't have Simmons No. 1 [on their draft board] should be fired," one longtime GM with a great draft track record told ESPN on Monday.

Fifty-one NBA scouts and execs attended Simmons' game in Brooklyn on Monday in which he had 21 points, 20 rebounds and seven assists.

"You don't find players his size, with his elite athletic ability that see the game the way he sees the game," one GM said. "He's unselfish to a fault. He's always trying to make the right play. And he's just scratching the surface. Look at how the other freshmen are faring right now. It takes a while to adjust. What does his box score start looking like when he adjusts?"

The main concern with Simmons is his jumper and whether that may make a team pass on him at No. 1 was asked.

"Not a chance," one GM said. "He does everything else well. He's not a bad shooter. It won't stop anyone from taking him No. 1."

Skal Labissiere, Dragan Bender and Jaylen Brown could all compete for the No. 1 spot.

"Towns, Mudiay and Porzingis were always in the mix last year," one GM said. "There was plenty of debate. There just isn't any real debate with my scouts about Simmons right now. He's way ahead of those guys. He's going to have to struggle and those guys are going to have to get a lot better."

Labissiere has ranked No. 1 on the Draft Express' Big Board since last April.