NBA-best Celtics hit the road with a target on their backs and room to improve on a six-game trip

Coach Joe Mazzulla has the NBA-leading Celtics pointed in the right direction at 18-5.Barry Chin/Globe Staff

NEW YORK — The Celtics are in a fascinating place entering one of their most fascinating road trips in recent years.

Boston begins a six-game journey through the East and then West on Sunday in Brooklyn, possessing the best record in the NBA and coming off their third overtime loss of the season Friday against Miami.

The good news is the Celtics played rather poorly, had a season-worst game from Jayson Tatum and committed 20 turnovers, yet led by 8 points in the final period.

“When you’re in great positions against great teams, you have to execute,” Celtics coach Joe Mazzulla said. “I thought it was two good teams playing against each other. We have to learn how to manage games against great teams.”

This is a critical trip for the Celtics, especially for Mazzulla, who will have to encourage his team to respond to difficult road venues because they are now the target.

They are the defending Eastern Conference champions with one of the league’s best players and an offense that has been phenomenal for the most part.

The Celtics have to approach this trip with an angry and determined mind-set. They should be angry about Friday’s loss because they wasted chances to win. They should be determined to win all six games on this trip because they can still be better.

Robert Williams is getting healthier and should be back by month’s end. The Celtics have won 18 of their first 23 games without him. It’s one thing to beat up on Eastern Conference opponents, to take advantage of a homestand with wins over the Heat, Charlotte Hornets and Washington Wizards; it’s another to head west to play the Phoenix Suns, Golden State Warriors, and both the Lakers and Clippers in Los Angeles and walk away with victories.

The Celtics will be away from Boston for 10 days, to visit the rival Nets and Toronto Raptors, then the Suns, who have the best record in the West, before a Finals rematch with the Warriors. Similar to what the Heat did Friday, the Celtics have an opportunity to make a statement.

“We’ve just got to be better,” Marcus Smart said Friday. “When you’re playing against a team like (Miami) the marginal areas are going to be big. The margin for error is very small. You chalk this one up, look at the film, learn and come right back to work.”

If the shots aren't falling on the offensive end like on Friday against the Heat, Marcus Smart and the Celtics need to turn up the pressure on the defense.Erin Clark/Globe Staff

The Celtics are now the big game on the schedule, even for the Warriors. Teams around the NBA have been monitoring the Celtics’ progress, how well Tatum has played, the rise of Jaylen Brown, the improvement of Derrick White, the addition of a knockdown 3-point shooter in Sam Hauser, the continued production of Al Horford.

That progress has occurred without their best defensive players and rim protector in Williams. Opposing teams have been trying to gash the Celtics in the paint and Miami repeatedly went to center Bam Adebayo in the post during crunch time of Friday’s second game of a back-to-back set. But other than Friday, the Celtics have fared well compensating for the lack of a difference-making center, and this should be one of the last stretches without him.

What the Celtics are trying to avoid is being a team that only wins when shots are falling. They have to become better at grinding out victories when Tatum and Brown struggle offensively. The defense is gradually improving and has been a Mazzulla emphasis. The Celtics will have to win games on this trip with defense.

“We’ve got to continue to work, got to continue to find a way, especially when shots aren’t falling,” Smart said. “This isn’t going to be the last game like this. There are going to be other games. It’s best that we be able to learn this and figure it out and to be able to look at this film and look back and say, ‘We know what to do now and let’s go do it.’ ”

Sunday will be the first game this season against the Nets, who are playing well since Kyrie Irving returned from his suspension. Kevin Durant continues to play at an MVP level and the question is whether Mazzulla will defend Durant in the same stifling fashion as Ime Udoka did during last season’s playoffs.

The Celtics are a considerably better team than the Nets and better than the Celtics team that swept Brooklyn in that playoff series. But it’s important for Boston to punch first, to start with a defensive mind-set. Tatum has to bounce back from one of his worst games in recent memory, and the club has to take care of the ball.

There are plenty of issues for Mazzulla to fix in the next 10 days. The Celtics were probably helped by that Miami loss because it exposed those weaknesses, and they begin this journey vulnerable but motivated.