‘We have to get sharper.’ The Celtics turned aside the scrappy Pacers, but it wasn’t easy

Celtics forward Jayson Tatum battles for a rebound against the Pacers during the first quarter.Barry Chin/Globe Staff

Jaylen Brown and Jayson Tatum missed Monday’s game against the Raptors to rest their knees, Al Horford sat out for personal reasons, and Robert Williams was sidelined due to his knee injury, removing four-fifths of the NBA’s most dominant starting lineup.

Williams remains out, but the other three returned this week. And although a night off this late in a long, grueling season would seem to be beneficial, coach Ime Udoka said things have subsequently been clunky.

“Since they came back from the game they missed in Toronto, we haven’t been on point in the last two games,” Udoka said. “We’re going to have to definitely get that together.”

Earlier this season, disorganized play would have resulted in a frustrating loss. But the Celtics did well to steady themselves and have reached a point where they can squeeze out wins even when they are not necessarily at their best.

That’s what happened Friday night, when they held off a mediocre but eager Pacers team and eventually secured a 128-123 win. Although it was another wire-to-wire victory for Boston, it did not feel as breezy as those that preceded it.

“We had a good stretch of double-digit wins, some easier wins, and lately we’ve had a stretch of tougher games,” Celtics forward Jayson Tatum said. “We can benefit from that, and I’m just glad we found a way and won the game.”

The Celtics (48-30) moved within a half-game of the second-place Bucks (48-29) and 1 ½ games of the first-place Heat in the Eastern Conference standings. Boston faces the Wizards at TD Garden on Sunday before closing the regular season with a difficult three-game road trip against the Bulls, Bucks, and Grizzlies.

The Grizzlies are locked into the No. 2 spot in the Western Conference, though, so they might not have any motivation to play their regular starters extensively in the season finale next weekend.

Regardless, Udoka and the Celtics understand it will be important to gain some momentum before the postseason arrives.

“We have to get sharper,” Udoka said. “No doubt about that.”

Jaylen Brown had 32 points for the Celtics, Tatum added 31, and Horford registered 17 points and 10 rebounds. The Celtics made 54.2 percent of their shots and snapped their first two-game losing streak since January.

At the start of this season the Pacers (25-53) figured to be among a group of teams tussling for space in the middle tier of the Eastern Conference. But they have been ravaged by injuries and they hit a soft reset button at the Feb. 10 trade deadline, and for the most part it has been a lost season.

So their game against the Celtics figured to offer a brief respite during an otherwise grueling recent schedule. Instead, Indiana scraped and clawed and made the Celtics’ elite defense look less fearsome than usual.

The Pacers made 51.9 percent of their shots and 47.2 percent of their 3-pointers. It was just the third time since Dec. 4 that a Celtics opponent has reached the 123-point mark, and Indiana has accounted for two of them.

In this case, it could create some cause for alarm since Boston was without its dominant, shot-swatting big man, Robert Williams, and he is unlikely to return from his knee injury until the second round of the playoffs.

“We know we’re a really good defensive team, and there’s a lot of areas tonight where we could have been better,” Tatum said. “Do we miss Rob? Of course. But our mistakes tonight weren’t because we didn’t have Rob. A lot of communication on the perimeter was our fault. We’ve got to be better.”

Tyrese Haliburton had a scorching but shortened night for the Pacers. He made 10 of 11 shots, 6 of 6 3-pointers, all four of his free throws, and finished with a team-high 30 points. But he dealt with foul trouble throughout the game.

Jayson Tatum gets a hug from his son Deuce after another Celtics win.Barry Chin/Globe Staff

He sat for an extended period after picking up his fifth foul with more than four minutes left in the third quarter, and soon after checking back in with just over eight minutes left in the fourth he fouled out while battling for position with Brown in the post.

At that point, the Pacers trailed just 103-101, and they did not wilt without their star point guard. A 3-pointer by Lance Stephenson pulled Indiana within 114-112 with 5:30 left. But they could never make a final push.

An Oshae Brissett 3-pointer with 1:26 left sliced Indiana’s deficit to 122-119 before Brown answered with a tough step-back jumper. After Brissett made one of two free throws, a Celtics scattered possession appeared headed toward a bad ending until Horford hit a cutting Tatum for a dunk just before the shot-clock expired.

Brissett hit another 3-pointer with 33.8 seconds left to pull Indiana within 126-123, but Derrick White answered with a driving layup.

“It was just one of those games,” guard Marcus Smart said. “Not every game is going to be pretty. We did enough to win, and obviously there are things we can clean up.”