The Boston Celtics didn’t skip a beat despite a long layoff following their first-round playoff sweep.

On Sunday, they simply went into Milwaukee and continued to roll in the next round.

Led by contributions from all over the roster, Boston carried over their momentum from the first round and scored a crucial road win to open the best-of-seven Eastern Conference Semifinals, toppling the top-seeded Bucks 112-90 at the Fiserv Forum. Gordon Hayward continued providing a spark off the bench, leading the Celtics’ second unit in scoring with 13 points, while adding four rebounds and five assists. Kyrie Irving led all scorers with 26 points and 11 assists in a dominant performance, while Al Horford also notched a double-double, with 20 points and 11 rebounds against a physical Milwaukee lineup.

While the scoring was a boon for Boston, the opening game, of what is sure to be a contentious series, was won on the defensive end. Milwaukee has proven to be one of the most difficult teams to handle in the league this season, led by superstar forward Giannis Antetokounmpo.

Milwaukee was also rolling going into Sunday’s game, having swept the Detroit Pistons in the first round by averaging nearly 122 points per game in their four wins. Their low output through that series was 119 points.

But Boston buckled down and kept them more than 30 points below their first-round average in Game 1 on Sunday with a strong team effort on defense. And they did it by limiting Antetokounmpo’s impact. The Greek Freak scored 22 points, but he did so on 21 shots. In fact, 14 of his 22 points came from three-point range or the free throw line as the Celtics kept Antetokounmpo out of the paint, where he is most effective. When he did get inside, Boston sent him to the line, where he made just 5-of-10 attempts from the charity stripe.

“We tried to guard Giannis as hard as we could,” Boston head coach Brad Stevens said. “He still ended up with 22 points and made a bunch of threes there in the second half, but that’s a team collective effort.”

On the offensive end, the Celtics found their rhythm early, outscoring Milwaukee 26-17 in the opening frame. After checking in midway through the frame, Gordon added to Boston’s lead with his first two points of the game with five minutes remaining in the quarter. The Celtics held the lead 13-8. Later, No. 20 drained a 17-foot jumper spurring a 10-2 Boston run that helped them hold a nine-point lead after one.

Gordon continued to impact the scoring column in the second, knocking down two buckets in a row, a 17-foot pull-up jumper and a floating jump shot, to extend the Cs lead to 12, 34-22 in the early stages of the second. His work leading the team’s second unit drew praise from coach Brad Stevens, who pledged to continue to assess the roles of each of his players as the series goes on.

“[I] wanted to keep Gordon coming off [the bench] and so we could play through some of his actions when those other guys went to the bench,” Stevens said. “So we’ll see how it looks when we go back and look at it on the film.”

But despite Gordon’s best efforts early in the second, Milwaukee bounced back with a stronger quarter overall, outscoring Boston 33-26. The Celtics’ lead went as high as 15 points, 40-25 midway through the quarter, but after a bucket by Aron Baynes got Boston to that 15-point lead, the Cs went cold. Milwaukee followed with a 15-0 run to tie the score with 3:26 remaining in the half. Gordon finally ended that run with an aggressive play that drew a foul on Milwaukee’s Brook Lopez, sending him to the line where he sank both free throws to give Boston a 42-40 lead.

That slim two-point advantage held at halftime with the Celtics in front 52-50.

After some halftime adjustments, Boston put it all together on offense in the third.

The Cs went on a 10-0 run early in the quarter to take a commanding 66-56 lead. With 1:53 left in the third, Hayward drained a three-pointer to add to the lead. With Gordon’s help, Boston’s edge climbed to 16 entering the final quarter.

Once again, the Cs’ battle-tested defense limited the Bucks to only 19 points in the fourth quarter, thwarting any possibility of a comeback. In the process, G created as many scoring opportunities for his team as possible. He had four of his five assists in the fourth. Irving and Brown scored seven points each and two of Hayward’s assists came on Brown’s baskets.

The Celtics were much more efficient on the offensive end than Milwaukee in Game 1, making 54 percent of their field goal attempts, compared to the Bucks’ 34.8 field goal percentage. Behind the arc, the Celtics made 41.9 percent of their shots to the Bucks’ 33.3 percent.

Boston knows that Milwaukee will respond in Game 2, and the Celtics will need to be ready for a battle on Tuesday to try and take command of the series before heading back to Boston.

“This is a hard team to play against and tonight wasn’t the best game,” Stevens said. “We’re going to have to be awfully good on Tuesday and we know that.”

Game 2 will be played in Milwaukee on Tuesday night. Tip-off is set for 8 p.m. ET, and the game will air on TNT.