The Celtics and Mavericks will tip off just after 8:30 p.m. in Game 5 of the NBA Finals tonight at TD Garden.

Here are the four big questions that will decide whether the Celtics win a title or head back to Dallas for Game 6:

1. How do the Celtics respond?

Joe Mazzulla warned his team days ahead of time.

“The closer you think you are to beating someone,” Mazzulla said last week before Game 3, “the closer you are to getting your ass kicked.”

Then came Game 4: Mavericks 122, Celtics 84.

Since suffering the third-worst loss in Finals history, the Celtics sound like they have lightened up and let go. Several players said they felt out of character Friday night, a bit tense and rigid with their go-for-the-kill mentality. Jayson Tatum relayed Sunday that Mazzulla recently told his players it’s “OK to smile in war,” and smile they did before a scheduled practice at TD Garden.

Last Friday wasn’t a war so much as a blitzkrieg the Mavericks used to prevent a stone-cold sweep. But the Celtics are more likely to find themselves in a war tonight, again facing a desperate Dallas team that’s rebuilt its confidence after falling into a 3-0 deficit. So how will Boston respond?

The Celtics should benefit from a crowd buzzing with championship anticipation, but that can only carry them so far. Effort alone doesn’t win titles. Famous for sometimes letting go of the rope, Boston cannot play with any sense of entitlement or lost focus Monday.

It’s a mental tight rope they must walk — playing with maximum effort and energy, not too little emotion or too much, and an acceptance of the pressure that comes with an impending title, without allowing that pressure to affect their play. The challenge of an aspiring champion.

2. What can they do to solve Dallas’ hybrid man-zone defense?

Tying together Games 3 and 4 — two wildly different basketball games with disparate finishes — was a unique Mavericks defense that toggled between man and zone.

Sometimes between possessions, sometimes between matchups and ends of floor. Rookie center Dereck Lively II is the keystone of this amorphous scheme, a springy 7-footer who can cover acres of ground, contest shots at the rim and dance in isolation on the perimeter.

Lively played by far his best basketball of the Finals in Game 4, when the Celtics’ offensive rating was a dismal 85.7 points per 100 possessions. There is some noise in those numbers — Svi Mykhailiuk won’t play 10 minutes tonight and Payton Pritchard won’t see 22 — but the point stands. Around a dominant quarter in Game 3, the Celtics’ offense has felt shaky for significant stretches the past two games, and the Mavs deserve credit.

To review: in Game 3, Dallas fast-tracked them to 30 points in the first quarter by allowing two fast-break buckets in the final minute, then held the C’s to 20 points over the second quarter. Boston throttled the Mavs in the third, then barely held on over the fourth by nearly blowing a 21-point lead. That bled into Friday, when the Celtics got to only 35 points at halftime.

To beat the hybrid zone, Boston will hoist plenty of 3-pointers Monday. But will they come from Jayson Tatum lazing into step-backs? Or will they spring from the humming drive-and-kick attack that broke Dallas’ initial defense in these Finals and has worked all season?

3. Can Boston wear Luka down again?

Through four games, Luka Doncic has scored eight points in the fourth quarter.

That’s right. Eight.

A lopsided score allowed Doncic to take a seat down the stretch of Game 4, but otherwise the Celtics have kept the perennial MVP candidate off the scoreboard by beating him up over the first three quarters. Boston has hunted him on defense and sent a rotating cast of physical defenders at him when he has the ball.

Expect Boston to continue seeking out Doncic — whose defense improved Friday night — in Game 5, with Tatum and Jaylen Brown calling for screens that put him directly into the action. The Mavs certainly are.

“He knows in Boston he’s going to be right back in the pick-and-roll,” Dallas coach Jason Kidd said after Game 4, “so he’s going to have to compete and play defense again.”

4. What role, if any, could Kristaps Porzingis play?

Again, Porzingis’ status remains a mystery.

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He was available for Game 4, according to Mazzulla, who said Porzingis could play in specific situations. Before Sunday’s practice, Xavier Tillman’s comments indicated those situations are probably very few.

“He’s doing some stuff, but you can still tell he’s very uncomfortable,” Tillman said of the big man.

So far this series, the Celtics are plus-25 in Porzingis’ 44 minutes. They are minus-31 with him off the floor. That number — like most for Boston — took a massive hit with Friday night’s blowout loss. Still, Porzingis completely changes Boston’s ceiling and optionality at both ends of the floor through his ability to punish switches, protect the rim and provide optimal spacing.

“We miss him a lot,” Holiday said Sunday. “(He’s a) top-three player on our team.”

Without him, Dallas took almost 40% of its shots in Game 4 at the rim. That number is untenable, unless the Celtics want to shoot 40% from 3. So even if Porzingis is limited to 5-10 minutes, he could swing Game 5 and help clinch a title.