Tobias Harris emerges as a spark plug for the Sixers in Game 1 vs. Brooklyn Nets

Tobias Harris is the 76ers’ X factor.

If the forward can continue to play like he did Saturday, the Sixers will be tough to beat this postseason.

Harris excelled on both ends of the court in the Sixers’ 121-101 Game 1 victory over the Brooklyn Nets in their first-round playoffs series.

“When Tobias is playing well, when Georges [Niang] has points, it usually means the ball is moving,” coach Doc Rivers said. “... I thought that it just showed that we were trusting the pass.”

Rivers is right. Harris excels when the ball is moving. But he was more aggressive than usual while finishing with 21 points on 9-of-14 shooting, including making all three of his free throws in the contest at the Wells Fargo Center on Saturday. Harris also had four rebounds, four assists, and a block in addition to shutting down Mikal Bridges in the second half.

The former Villanova standout finished with a game-high 30 points on 12-of-18 shooting. However, Harris held him to seven points on 2-for-2 shooting after intermission. Scoring opportunities were hard to come by in the second half.

“And tonight, in the playoffs is when you are going to have different matchups that teams are presenting out there — different matchups, different schemes,” Harris said. “For me, it’s just staying in the moment and being aggressive with all opportunities that come my way.”

As impressive as he was offensively, it was his defense that was the most impressive. Once regarded as a defensive liability, Harris has taken major strides this season. And he played the part of a lockdown defender in the second half of Saturday’s game.

Bridges attempted only one shot — a made 12-foot fadeaway jumper — in the third quarter. His last basket came in the fourth quarter.

Harris forced Bridges into harder looks.

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“He’s a hell of a player,” Harris said, ”and they run a lot of actions through him, which makes a lot of tough shots, contested shots. But as a group, that’s going to be a huge emphasis for us, going into Game 2, being ready time to stop them.”

Nets coach Jacque Vaughn thinks the game just slowed down in the second half, leading to Bridges’ lack of production.

“I thought that was the biggest difference,” he said. “For us, we have to keep this thing fast-paced, and it starts with stops. I thought he had a great first half for us to set the tone early and get into his spots, showed an array of shots.

“It’s on me to continue to get the ball to him and also continue to have pace when they’re not bogging him down and holding him and grabbing him and letting him not play with freedom of movement.”

But Harris did deny shooting opportunities. He’ll attempt to do it again on Monday.

“He’s really good,” Harris said of Bridges. “Got it going on, especially early in the game. We have to show a little different schemes defensively.”

If he can keep that up, this Sixers just might have the key pieces needed to win a title.