This is all about gravy.

This is about the Celtics in the Eastern Conference finals just one year after having won only 24 games, the very visible symbol of a franchise that seemed as gone as the ’80s.

This is about the Celtics in the Eastern Conference finals just a year after they were trying to get the first pick in the lottery, and the sense of despair that came when they didn’t get it, as if that were one more symbol of their descent into irrelevancy.

That’s the thing that shouldn’t be overlooked on the eve of this new series against the Pistons, the sense of how far this franchise has come in a year, the biggest turnaround in NBA history.

The sense that this is all about gravy.

For there is no more pressure on the Celtics — not really.

That went away Sunday with the win over the Cavaliers, all but running out of the building with LeBron and the rest of the Cavaliers.

Rest assured that if the Celtics had lost on Sunday, their season over, there would have been repercussions. Doc Rivers would have had a big fat target on his back, fair or not. The Big Three would be called little more than cardboard cutouts of the original Big Three, some dime-store imitation that couldn’t get it done when the stakes got raised. This team would be seen as a failure, unable to capitalize on its success in the regular season, unable to do what we expect great Celtics teams to do, a promise unfulfilled.

That was what Sunday was about, just as it was in Game Seven against the Hawks. Teams with the best record in the NBA are not supposed to go out in the first or second round.

Not in Boston, anyway.

Not in Boston, where expectations are as high as a Kevin Garnett fall-away in the lane.

Not in Boston, where the promise of this team was that it would play big games before this season died, games that get remembered.

That was the pressure the Celtics took into Sunday afternoon, the knowledge that everything they’d accomplished so far was all ephemeral, could disappear as quickly as a LeBron drive to the hoop.

There’s no underestimating that. Not in this day and age when it’s about winning or failure, with little in between. Not in Boston, where the Red Sox and Patriots have set the bar so incredibly high, and that’s not even talking about those 16 championship banners that hang in the rafters, the ultimate standard of excellence.

That’s the pressure that’s over now.

Or at least it’s been taken down a few notches.

To lose to the Pistons would be disappointing, certainly, especially when the theme of this season has become the quest for the 17th championship banner, not only validation for the new owners but the symbolic resurrection of this franchise.

But this is by no means a slam-dunk.

“You know, before the year, people thought it would be us and Detroit in the Eastern finals, and conference finals, and we believed that, too,” Doc Rivers said Sunday.

Rivers had been in the large interview room inside the Garden, and the relief seemed to almost come off him in waves. He knew what Sunday’s game had meant, its importance, not only to his team, but to himself, too. He knew that if the Celtics had lost Sunday, the fingers would be pointing in all sorts of directions, his included.

Left unsaid was the fact that the pressure is gone now.

For the Pistons come in here having now been to the conference finals six straight times. They have been the best team in the East for a while now, a veteran squad that won an NBA title in 2004, and has been in a lot of huge games. And even if they got upset last year by the Cavs in the Eastern finals, when LeBron did to them what he almost did to the Celtics on Sunday, they’re still the gold standard in the Eastern Conference, still the team with the resume, still the big dog.

And if they’re not quite the defensive team they’ve been in the past, the Pistons still are everything the Celtics are not — experienced in playoff games, a core of players that has been through everything together, a team that has won so many big games before.

Rivers had talked about that after the Atlanta series, the fact that this is the first trip through the playoffs for this Celtics team, regardless of the fact that some players on the roster have been in the playoffs before.

That had been the thing no one ever seemed to talk about when the playoffs started, the fact that this was all uncharted territory for this team, the fact of NBA life that there is the regular season and there is the playoffs, and sometimes the two don’t have a whole lot to do with one another.

That’s what got so complicated in the first two rounds when the Celtics failed to win any games on the road. It was a danger sign, no question about that, a sign of flaws, ones we weren’t aware of. It’s what took the first two rounds to seven games, the NBA version of walking on a tightrope in the dark, complete with the sense that one bad step, one bad game, one more LeBron three at the wrong time, and everything changes — a season, reputations, all of it.

That is what the Celtics escaped on Sunday, and the collective sigh you hear is the pressure escaping like steam through a manhole cover.

That was the real work.

The Celtics back in the Eastern Conference finals a year after they won just 24 games, the biggest turnaround in the NBA’s long history.

And now?

This is all about gravy.

breynold@projo.com