Yet, just because the Celtics are at home does not automatically equate playing better or the Mavericks succumbing to make this a neat and convenient story line. Boston will have to earn this win with perhaps its best performance of the season.

The Mavericks have little to lose because they are expected to lose.

No prognosticator picked Dallas to win the championship when the season began. The Mavericks are the underdogs. They are loose, knowing every victory they steal puts more pressure on the favored Celtics. This indeed has turned into a mind game.

Boston wants a title, it needs a title. The city can taste it.

“I don’t look at it as pressure,” Tatum said Sunday before practice. “I do notice, especially this time of the season, playoff time and obviously being in the Finals for the second time, when you drive around and go to the gas station, or I wanted to go get some ice cream yesterday, it’s Celtics gear everywhere and everybody is super excited about this team and what we have accomplished and what we have the chance to accomplish. You really just feel the love and support from everybody in the city of Boston, and how bad they want us to win, how much they have been cheering for us.

“So I don’t look at it as pressure. Just unconditional support, and that we have an amazing fan base here.”

The hunger is there, the players say, although it didn’t appear that way Friday. After saying they had to play like the more desperate team in Game 4 even though they weren’t, the Celtics played about six good minutes before they relented to the team that was really desperate.

There’s something to playing with zero expectations and the Mavericks have embraced that role. They are highly unlikely to come back from a 3-0 deficit. No team has done that in 156 tries, but that doesn’t mean they can’t cause angst and discomfort for their opponent in the process.

“Sometimes when you do play an opponent over and over, you get used to the tendencies and you start to capitalize on that on both ends, defensively and offensively,” Dallas coach Jason Kidd said. “Hopefully our group has seen enough of Boston to understand what they are good at, and hopefully we can take that away (Monday) night.”

Monday will be the most difficult game of the Celtics’ careers because it’s the most significant. But it’s also important to remember they still hold the advantage. A team that hasn’t lost more than two games in a row all season would have to lose four consecutive games to lose this series. But there has to be a better sense of urgency than in Game 4. The Celtics have to feed into the crowd’s enthusiasm, play a more disciplined and passionate game, and let their talents and coaching take over.

“We have a great group, resilient group, and we don’t like to lose,” Brown said. “We do our best to prepare each and every night, each and every game, and we look forward to the next game on the schedule. I think we are ready for Game 5. I think that’s the best answer that I got. I think that we’re ready. We’re at home, and we’re looking forward to it.

“This is what we all work for. We are at the precipice of completing what we set out to do at the beginning of the season. So I think it’s not difficult to get everybody in that locker room on the same page right now. It just needs to remind everybody that it’s just one possession at a time. We do it together and we fight like our lives depends on it, and I think we’ll be all right.”

The Celtics lacked that fight in Game 4 and they can no longer take these games for granted. These chances to clinch are rare and they have to play their hardest, if not their best. That’s all this fan base can request. The Celtics owe their fans their best effort and an increased sense of urgency because they have a chance to achieve a career-defining accomplishment.

“[Coach] Joe [Mazzulla] did a great job today of reminding us that it’s okay to smile during wars,” Tatum said. “It’s OK to have fun during high-pressure moments. That’s what makes our team unique and special. We would love to win (Monday), more than anything. But if it doesn’t happen, it’s not the end of the world. We have more opportunities. So just setting that table of don’t surrender to that idea that we have to win tomorrow. We would love to, absolutely. But Game 5 is the biggest game of the season because it’s the next game on the schedule.

“So going with that mind-set, and just have fun. That’s really what we talked about today. Get back to having fun and being a team and how special we are and the team that got us here.”

Gary Washburn is a Globe columnist. He can be reached at gary.washburn@globe.com. Follow him @GwashburnGlobe.