It’s to the point where a loss Sunday at TD Garden would be a major disappointment for the Celtics’ season. Yes, no one outside that locker room expected this team to scratch and claw — mostly with home wins — to within one game of the NBA Finals.

It’s been a wildly successful season considering the injuries, setting up an expected title run in 2018-19. But with a 3-2 lead in the Eastern Conference finals, two chances to win one game, for the Celtics to fall short would be a major letdown.

This is the case especially since the Celtics have proven capable of beating the vaunted Cleveland Cavaliers. In past years, the Celtics just couldn’t compete with LeBron and Crew. They went 1-8 in their two previous playoff series losses.

They were embarrassed at home in the first two games of last year’s Eastern Conference finals, losing Games 1 and 2 by a combined 57 points, exemplifying the large gap between the teams. Even with Isaiah Thomas, who was injured during Game 2, the Celtics were no match for the Cavaliers. They needed to improve.

A year later, even without Kyrie Irving, Gordon Hayward, and Daniel Theis, the Celtics are not only on the Cavaliers’ level but better in many areas, younger, more athletic, and more resilient. The Cavaliers have been carried in this series by the amazing LeBron James and he may be good enough to get the Cavaliers to the Finals.

But if that happens, if the Celtics lose to LeBron, their reaction should not be just the tipping of the cap to an all-time great. They’ve had their chances to win this series. They even had their chances to win Game 6 when James scored 46 points.

The Celtics missed nine free throws, were outscored, 18-7, in second-chance points, and again suffered through a disastrous quarter, this time getting outscored, 34-18, in the second period. LeBron was superb in the final minutes of the game with his back-to-back 3-pointers from the same spot on the floor, but the Celtics had a chance to prevent it from getting to that point. They botched the opportunity.

The Celtics are no longer the upstart team this deep into the playoffs. They are one strong game from reaching the NBA Finals. They have proven to be better than the Cavaliers in most stretches of the series, especially at home. They have been burdened, however, by one poor stretch or lack of execution at key sequences.

That has little to do with inexperience and more to do with carrying out the game plan. The Celtics have to stick to their convictions, defend well, not be concerned with the absence of Kevin Love, because Jeff Green and Larry Nance Jr. each have had their moments.

“Like I just thought we did a lot of good things [Friday] that we can build off of,’’ Celtics coach Brad Stevens said. “Just like we said all year, tomorrow it’s not going to be perfect. You just go in there, you compete, you play as hard as you can, and let the chips fall where they may. You just have to have perfect intentions.’’

The Celtics are favored Sunday and they should be. The Cavaliers aren’t a great team. They are LeBron and the Inconsistents, with James fully realizing he has no idea who will flourish in the Game 7 moment — besides himself.

“You’ve got to be poised. You’ve got to be able to handle a punch or two,’’ James said of Game 7. “And you’ve got to be able to combat that and be just as solid and just as aggressive on the offensive end. We know it’s challenging. They’re 10-0 on their home floor, and they’ve been very successful against us, obviously, at home. But if you love challenges, then this is a great opportunity.’’

Without Love, the Cavaliers’ second All-Star and second-leading scorer, Cleveland will have to rely upon players who have seldom been asked to deliver in such a pressure situation. The past Cleveland teams were lined up with proven veterans. Irving could deliver on nights when James was subpar. Last year, the Cavaliers had three players average more than 20 points in the Celtics series. Only one of those is playing for Cleveland on Sunday, LeBron James.

It’s lazy to believe that simply being at home will win this series for the Celtics. They will have to play well. They will have limit mistakes and get Al Horford involved early and they will have to understand that James is going to give an absolute supreme effort to avoid potentially his last game as a Cavalier being at TD Garden — again.

The Celtics are beyond the point of playing with house money. They have a chance to reach the NBA Finals and those chances are not to be squandered. It’s good for the Celtics to be home. But they are the better team and need to play like it. If not, this will be a disappointing end to a remarkable season.

“You’ve got your fans behind you. It’s a whole different feeling when you’re playing at home,’’ guard Terry Rozier said. “You’re just so amped. Our crowd is unbelievable, one of the best in basketball. We’re looking forward to it. It’s going to be a lot of fun. Like Coach said, it was the best two out of three. We’ve got to go back home for Game 7, and we’ve got to take care of business.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter at @GwashburnGlobe.