KISSIMMEE, Fla. – Very few people outside of the 76ers’ locker room are giving the team a chance in its upcoming showdown against the Boston Celtics.

The expectation is that Boston will make light work of the Sixers in the Atlantic Division rivals’ opening-round playoff series.

Despite the Sixers winning three of the four regular-season meetings, the thought is that Ben Simmons’ injury and the team still trying to figure things could lead to a quick playoff exit for the Sixers. Game 1 of the best-of-seven series is 6:30 p.m. Monday at The Field House at Walt Disney World.

“To be honest, we don’t care about anybody else’s opinion but ours‚” Tobias Harris said before Sunday’s practice.

Harris revealed that the sixth-seeded Sixers are confident, internally. The players know what they bring to the table. They expect a lot from one another. And they’re only worried and focused on themselves, not the outside noise.

“At the end of the day, it’s all about what we do in our locker room,” Harris said. “That’s what we are focused on.”

The Sixers’ depth and everyone coming together for a common goal gives Harris confidence heading into the series. The veteran forward feels the Sixers have had a great vibe playing together. He will also tell you that the team’s competitiveness and focus is there.

“And we’re ready,” he said. “As a unit, coming out here to Orlando, this is our goal to get in the playoffs and do what we have to do. We’re excited for that.”

But center Joel Embiid might have to play at an MVP level for the Sixers to advance to the second round.

The 7-foot-2 three-time All-Star could take advantage of his 6-inch height advantage over Celtics center Daniel Theis. Opposing centers have had their way with the third-seeded Celtics this season.

“Embiid is a one-of-a-kind type of talent that you don’t see very often,” Boston guard Jaylen Brown said Sunday. “So we have to do our job and do our best to slow him down and make him have a tough night.”

Boston expects Embiid to come out and dominate and establish his own space. That’s why Brown said it’s important for the Celtics to execute their game plan.

“Hopefully, he has an off night, an off couple of nights,” he said.

The Sixers hope Brown and the Celtics’ other perimeter starters have some off nights of their own.

On paper, Philly doesn’t match up defensively against Boston’s four starting perimeter players.

All-Star Jayson Tatum averaged a team-leading 23.4 points to go with 7.0 rebounds and shot 40.3% from three in the regular season. The 6-foot-8, 210-pounder is listed as a power forward in Boston’s wing-heavy, small-ball starting lineup. His athleticism and quickness make it hard for traditional post players to guard him.

All-Star point guard Kemba Walker averaged 20.4 points while 38.2% on threes. Brown made 38.1% of his threes and averaged 20.3 points. And small forward Gordon Hayward added 17.5 points, while shooting 38.3% from long range.

In addition to not having Simmons (knee surgery), the Sixers are most likely to be without Glenn Robinson III (oblique muscle strain). Robinson will be re-evaluated in seven to 10 days.

“You don’t have the luxury of a misstep or a mistake, a lack of a proper read,” coach Brett Brown said of playing without Simmons and Robinson.

However, the coach, like Harris, was outwardly confident before Sunday’s practice.

Embiid is arguably the NBA’s best center when healthy, in shape, and motivated. Philly also has highly paid forwards in Harris and Al Horford, a former Celtic. That’s why Brett Brown double-downed once more about his team being built for the playoffs. He reflected on how the team has transformed from tanking to its current state of being a perennial playoff team.

“Obviously, now the goal and the standard is you win a championship or you don’t,” he said. “I believe that we have, even without Ben, I believe we have a team that’s capable of doing that.

“And I’m excited to go play the Boston Celtics.”