WALTHAM, Mass. -- For the better part of three seasons, the Boston Celtics have been fueled largely by the perception of disrespect. As such, they found the perfect postseason rallying cry when it was suggested that Boston might be one of the worst No. 1 seeds in recent history.

"I watch TV, so I see all the B.S. that they talk, and they're counting us out already," Celtics All-Star point guard Isaiah Thomas said. "I'm used to it, I guess. It's just crazy.

"Nobody gives us our due. We're the No. 1 seed, and then they say we're one of the worst No. 1 seeds. If anybody else was the No. 1 seed, it'd be like, 'They might get to the Finals.' It's always something, but we try not to worry about that stuff and just try to take care of business on the court."

Thomas said he went into social media hibernation earlier this week but has seen analysts downplaying Boston's postseason potential, despite a 53-win season that helped the team finish two games ahead of the defending champion Cleveland Cavaliers.

Celtics coach Brad Stevens has repeatedly noted how much of Boston's success can be traced to chip-on-the-shoulder players such as Thomas and Jae Crowder. As the Celtics prepare for Sunday's Game 1 against the eighth-seeded Chicago Bulls, they rallied around the notion that few believe they are true title contenders.

"Our motivation is to win a championship. That's enough motivation in itself," Crowder said. "We're not expecting everyone to be on our side. As long as the guys in the locker room believe and our coaching staff believes in us, we've been able to get the job done night in and night out.

"We're just believing in ourselves. We don't need anybody else to believe in us. We believe in each other, so we'll let that handle itself."

Additionally, the Celtics will be playing with heavy hearts following the death of Thomas' sister in their native Washington.

Isaiah Thomas and the Celtics believe "nobody gives us our due," even after they earned the top seed in the Eastern Conference. Winslow Townson/USA TODAY Sports

Many have wondered about Boston's overall potential, especially after first-round exits the past two seasons. Others point to how Cleveland prioritized rest over seeding at the end of the regular season and suggest it's the only reason Boston emerged with the top spot. That's all Boston needed to prolong its us-against-the-world mentality.

"We're kinda used to this," Marcus Smart said. "Everybody on this team has been underdogs. That's why we've been doing so well: because we always play with a chip on our shoulder. We expect that. We're not really worried about it. We're just focusing, like I said, on what we can control.

"You look at us on paper, you wouldn't think that this team would be where we're at in the standings and all that and accomplish all the things that we've accomplished, the things that we did this regular season. That just shows how much heart we have and the chip that we do carry on our shoulders because of that."

Stevens certainly believes in his team, but he probably isn't too upset to see them find some extra motivation heading into the playoffs.

"I think that's been one of the reasons why we've been at the level we've been at -- not only this year, but being able to come together in the last 15 months before that and play with a chip on their shoulder," Stevens said. "If there's anything that would have been used to describe this group of guys, both early on and throughout, it's they have a chip on their shoulder.

"We're going to have to play that way once the games start [Sunday] because every team is tough, and you gotta play well to win."