Sixers' Ben Simmons keeps competitive fire under control | Keith Pompey

It's going to be interesting to see Ben Simmons' competitive spirit in the Eastern Conference semifinals.

NBA fans may start drooling if it's anything close to how the 76ers rookie point guard played against the Miami Heat in the conference quarterfinals.

"He was a quiet killer," Sixers coach Brett Brown said. "He really was a silent assassin in many, many ways."

Simmons didn't overreact to the borderline cheap shots he received from the Heat. The only time Simmons got in an opponent's face was when he stepped toward James Johnson in Game 4 to protect teammate Robert Covington. Other than that, the rookie-of-the-year candidate went about his business in a very physical and methodical way.

"It's sound like it's complacent and it's not meant to; he's just steady," Brown said. "It's just a steady drumbeat "

Simmons' poise and play in the postseason have been remarkable given his lack of experience.

The 21-year-old from Australia is averaging 18.2 points, 10.6 rebounds, 9.0 assists, and 2.5 steals through five postseason games.

Simmons collected 17 points, 13 rebounds, 10 assists, and four steals in a Game 4 victory over Miami, becoming the fifth rookie to ever register a triple-double in a playoff game. He also became the first Sixer since Charles Barkley on April 27, 1991, to record a postseason triple-double.

He joins Hall of Famers Magic Johnson, Kareem Abdul-Jabbar, Jerry Lucas, and Tom Gola as the only rookies to record postseason triple-doubles. Johnson, in 1980, was the previous rookie to accomplish the feat.

Simmons was asked what he learned about himself after the Sixers closed out the Heat, 4-1, on Tuesday night.

"That I'm ready," he responded. "I'm ready for the playoffs."

But he and the Sixers know things are going to get tougher starting Monday

That's when they'll face the Boston Celtics, who defeated the Milwaukee Bucks, 112-96, in Game 7 of their conference quarterfinal is Saturday night at TD Garden in Boston. The Celtics get home-court advantage and host the Sixers in the conference semifinals at 8 p.m. Monday.

Simmons held his own against Boston in the regular season. In four games against the Celtics, he averaged 12.5 points, 6.5 rebounds and 5.5 assists a game. As a result, one can only assume that he'll continue to compile solid numbers. Despite his hesitancy to shoot, he is still tough for teams to defend. Always a solid passer, Simmons is doing a better job of creating easier shots for teammates. He has mastered passing the ball to where they're going to be in transition instead of where they are. And he proved a while ago that he can guard opposing point guards. His 6-foot-10 frame actually creates problems for the smaller guards.

So there won't be a problem when it comes to strictly basketball. But the postseason isn't just about basketball skills. There's a mental game that involves trying to frustrate opponents.

That was evident from the start in Game 5 against the Heat.

Simmons drove into the lane 1 minute, 31 seconds into the game for a layup attempt. He appeared to turn the corner on Johnson. But that's when Josh Richardson did his best free-safety impersonation. Richardson went low at Simmons, taking out his legs. Simmons flipped in the air and landed on his back. He popped up, motioned to his teammates to calm down, and walked briskly to the other end of the court and back.

Then he went to the foul line and made a pair of free throws to give the Sixers an 8-3 lead.

Early in the third quarter, Heat point guard Goran Dragic displayed his frustration. He fouled Simmons after the rookie stole the ball from him. Then Dragic clearly slapped Simmons in the back of the head, drawling a technical foul.

"It's bigger than that play," Simmons said of maintaining his cool after Dragic's slap. "The whole game is bigger than that play. For me, I can't get caught up in that. My team needs me on the court."

The Sixers will  definitely need him on the court in the semifinals. And his next opponent will definitely attempt to mentally get him out of his game.

That's why his competitive spirit will be closely watched.

But Simmons just plans on focusing on the next play in what is expected to be a physical series.

"Every individual incident is actually not as big as the actual game," he said. "So if I'm able to keep my poise and carry on with my team and keep playing the way we are playing, we will be fine."

The former Louisiana State standout doesn't go into games bracing for something to happen.

"I'm just playing, honestly," he said. "Whatever they throw at me, I'll be ready for it. At the same time, I'm not going to get too crazy or lose myself in that moment. I've got to stay present for my team."