There was an understandable expectation that the Celtics’ new-look starting five would need a little time to jell this season. Even with all this talent, it wasn’t entirely realistic for the chemistry to be built right away.

They’re starting to debunk that theory.

While their first two victories of the season required some grit and toughness, the Celtics and their stacked talent have begun to exert their will on opponents, showing how scary good they can be. For a second consecutive game, they took care of an inferior team with extreme ease. Sparked by another hot start, the Celtics dominated the Pacers – who were without All-Star guard Tyrese Haliburton – with a 155-104 victory at TD Garden that was never in doubt from the opening tip.

The 155 points mark the second-most the Celtics have scored ever in a regular-season game, only behind the 173 they scored in a win over the Minneapolis Lakers on Feb. 27, 1959

Jayson Tatum scored 30 points with 12 rebounds, Derrick White had 18 points and Sam Hauser scored 17 points on five 3-pointers off the bench in the rout. Like Monday in Washington, D.C., the Celtics rested their starters for the entire fourth quarter. Each of the players in that group played 27 minutes or fewer, which could have long-term benefits for the Celtics with how much they will rely on that group throughout the season.

Celtics coach Joe Mazzulla has been emphasizing a renewed mindset of toughness and focus for his players, and it’s already paying off. They needed it in crunch time of their close opening victories over the Knicks and Heat. And once vulnerable to horrible losses to inferior teams, the Celtics have not overlooked their opponents this week.

On Wednesday, they took it to a different level.

The Celtics, too often last season, were guilty of letting go of the rope against inferior teams to them. Even when they built big leads, they lost focus and lost them. So far this season, they’ve made sure that’s not a problem.

The Celtics led by 21 at halftime after another blistering hot offensive first half and kept their foot on the gas pedal. They opened the second half on a 12-1 run to open their lead to 32. There was never a threat of a comeback as they led by as many as 53 late in the fourth quarter.

Like they did against the Wizards on Monday, the Celtics lit up the Pacers in the first quarter with another torrid shooting display. They trailed 6-4 in the opening minutes before reeling off a 14-0 run behind stops and 3-pointers from White, Jrue Holiday and Tatum. That forced a Pacers timeout but the Celtics continued to find mismatches and extra spacing inside as Kristaps Porzingis and Jaylen Brown flew in for easy dunks.

The Celtics carried that momentum. They were almost unstoppable offensively. The Pacers entered the night allowing the fewest 3-pointers per game, but they hadn’t played an offense as potent as the Celtics, who hit eight treys in the first quarter. They shot 76.2 percent in the first quarter as they opened a 17-point lead over the helpless Pacers.

Tatum had no problem picking apart the Pacers’ defense, whether it was in the post, from the 3-point line or through driving lanes. He hunted mismatches on Pacers guard T.J. McConnell to score with ease on several possessions. He scored 12 points in the second quarter, including a step-back 3-pointer to give the Celtics a 23-point lead late in the first half.

The Celtics scored 75 points in the first half Wednesday, two shy of their first half total on Monday in Washington. It’s believed to be the first time in franchise history that the Celtics put up at least 75 first-half points in back-to-back games.