The Celtics and Mavericks will tip off in Game 3 of the NBA Finals tonight in Dallas.

Here are the four big questions that will decide the winner:

The Mavericks’ only paths to victory in the Finals — especially the direct ones — involved Kyrie Irving establishing himself as a top-3 player in this series.

So far, he’s been outside the top six. Maybe eight.

Irving’s averaged 14 points per game, gone 0-of-8 from deep and at times had trouble driving past Jrue Holiday, Derrick White and Jaylen Brown. But following his future-Hall-of-Famer track record, and even his history in these playoffs (21.9 points per game, 47% shooting overall and 39.1% from 3), Irving will break out soon.

But, if the Celtics can delay Irving’s return to form for a night, they should lock up the Larry O’Brien trophy. No NBA team has ever overcome a 3-0 series deficit in the playoffs. Without Irving at his peak, Boston’s depth has overwhelmed Dallas, as demonstrated by a plus-24 point differential through two games despite iffy 3-point shooting.

The Celtics have also devoted significant attention to Irving defensively, something he could turn against them by unlocking open 3s for teammates on kickouts, a la the Mavericks’ second-round series versus Oklahoma City when he averaged an extra assist per game and PJ Washington and Derrick Jones Jr. shot lights out. More than any other player, Irving is the switch that could flip Game 3.

Again, a lower-leg injury for Porzingis has Celtics’ fans holding their breath.

Porzingis limped off the floor late in Game 2, after which he and coach Joe Mazzulla insisted he was fine. Try again.

He is now considered day-to-day and officially listed as questionable after suffering a tendon dislocation in his left foot/ankle.

“I felt something, and now I have to deal with it,” Porzingis said. “As we said, yeah, it’s going to be day-to-day, and I’ll see how I am tomorrow. And obviously I’m going to do everything I can to be out there tomorrow, and we’ll see.”

Mazzulla called it “a serious injury,” a significant departure for the usually tight-lipped headman. If Porzingis does play, it’s unclear what risk, if any, he would incur of greater injury. Like Game 1, it also may not be until midway through the first quarter that we know whether Porzingis is at full strength or not Wednesday. Assuming Porzingis returns, expect Dallas to hunt him in space early.

The Celtics have been comfortable on a couple occasions leaving him on an island to dance with Irving and Luka Doncic in isolation. More of those possessions will test his lateral movement and pull him away from the rim, where Boston has done an excellent job limiting Maverick drives and lob dunks.

That rim protection, again, all starts with health. A healthy Porzingis completely changes Boston at both ends, not to mention protects their depth.

Take it from the man himself.

“I understand that I do need to be more efficient. I do need to shoot the ball better, I would not disagree with anybody on that,” Tatum said Tuesday. “But I’m not letting it bother me. I’m still trying to find ways to impact the game and dominate the game in other areas.”

Tatum went 6-of-22 in Game 2, when he attempted more shots than any other player on the floor. He was nonetheless effective because of his dozen assists, seven of which found Jrue Holiday, who rescued Boston at both ends. Tatum also snatched nine rebounds, another checked box in his favor that didn’t negate the 16 missed shots or playing occasionally iffy defense, but on balance left him with a passing grade for Game 2.

Now, better shooting can take that grade from passable to good … and maybe great.

Dallas’ top wing defenders — Washington and Jones Jr. — can’t contain Tatum or Jaylen Brown off the dribble, let alone Doncic or Irving when they’re forced to defend in switches. Tatum’s demonstrated willingness to drive repeatedly into crowds and Boston’s 82.9% field goal percentage at the rim should at least have Dallas on its heels in Game 3. That  would create more shooting space for Tatum, who could also attack in the mid-range, an area he’s hardly exercised against the Mavs.

Will he take advantage?

Back at home.

Backs against the proverbial wall.

The Mavericks will play with an energy and zeal the Celtics have not yet seen from them, the type of desperation a team cannot fake or weaponize until it’s trailing in a series. Two full off-days should also do Doncic some good, as he deals with injuries to his ankle, knee and torso. And all of that energy and recovery and frenzy will surface immediately in the first moments, an anxious crowd roaring and Dallas’ role players looking to contribute early to find a rhythm.

The key for the Celtics will be surviving those first few minutes, the first quarter and half. Doncic has worn down significantly as play has wore on this series, scoring just six total points in the fourth quarter. The longer Boston hangs around, the better off it will be.