A year ago, Matt Miazga was a raw teenager following glimpses of promise with glaring mistakes that cost goals — and games. But this season he has improved every game and was the best player on the field Friday for the Eastern Conference-leading Red Bulls.

“Matt’s gotten better every single game, and now this is his best performance,’’ coach Jesse Marsch said. “One, his aerial duels, he was reading plays well. When he had to make tackles, he made tackles. He was good with the ball. He was one of the best players, no doubt.”

Make that the best, according to whoscored.com, an analytics-based scoring system that rates players on a scale from zero to 10. Miazga’s 9.1 in Friday’s 2-0 rout of San Jose at Red Bull Arena was a stellar score and the highest for either team.

“We battled better than we did against D.C., because D.C. came out last week and kicked the crap out of us, and I don’t think we responded well enough to protect each other and fight back,’’ Sacha Kljestan said. “[Friday] we were pretty good winning the battles. Matt Miazga won 99 percent of his head balls and so did Damien Perrinelle. That sets the tone.’’

Miazga, 19, won eight aerial battles, made four tackles, intercepted seven passes and had eight clearances, leading the Red Bulls in every category. From his scything tackles to his dominance in the air to his comfort on the ball — spinning around Chris Wondolowski — the tone was set, loudly and clearly.

“Every time I get an opportunity, I have to be mentally strong, ready to perform and contribute to the team. … I can’t feel pressure, I can’t feel nerves,’’ Miazga said. “As each game passes, I feel more and more confident. I feel I can talk to the guys. Even though I’m young, I can try and show my leadership qualities every game.”

To the point that, even with nominal starter and former English Premier League player Ronald Zubar on the verge of returning from the hamstring injury suffered in the season opener, Miazga made Marsch’s decision tougher.

“Yeah, it does. You’re absolutely right,’’ Marsch said. “It does make it tough and that’s the job of a coach to make tough decision.’’

Miazga left the Red Bulls to join up with the U.S. Under-20 national team for a training camp and friendly, but is expected back in time for the next MLS game against the defending champion L.A. Galaxy.

“Now when I go to the U-20s they’re going to be all my age, all the guys, I really can become a leader there,’’ Miazga said. “Coach [Tab Ramos] can put a trust in me to perform and close out games.”

Why not? His Red Bull coach already does.