Celtics coach Doc Rivers talks with Kevin Garnett in the second half of Sunday’s game in Los Angeles.

AP / Kevork Djansezian

It’s not supposed to be easy.

That’s been Doc Rivers’ mantra to his team throughout these playoffs. The fact that this is the NBA, these are the playoffs, and it’s not supposed to be some cakewalk, other teams merely lying down and throwing roses at the Celtics’ feet as they march toward an NBA title.

It’s not supposed to be easy.

That was what he told them when they had to go seven games to beat Atlanta, when the rest of the basketball world was wondering why it was taking so long. It was what he told them when they had to go seven games to beat Cleveland, when the basketball world was wondering why they couldn’t win any games on the road in the playoffs.

It was what he told them when they went into Detroit and won two games, back when no one ever thought they could.

It’s not supposed to be easy.

It’s probably what he told them after Sunday night’s game in Los Angeles, in which they came so close to closing out this series in just five games and winning their first NBA title in 22 years.

It’s not supposed to be easy.

No, it’s not.

Not when you’re trying to win an NBA title just a year after winning only 24 games, little more than an afterthought on the New England sports scene.

For this is winning the NBA title, and to do that you have to survive four rounds of playoffs, all with their own different matchups, their own different challenges, their own different pressures. This is winning the NBA title, an odyssey that starts during training camp in October and lasts for nine months, with its endless games and endless travel, if it’s Tuesday it must be Cleveland.

This is winning the NBA title, and it’s not supposed to be easy.

But for a while there Sunday night, it looked like it was going to be. The Celtics had won Game Four, coming back from a 24-point deficit to do it, and Sunday night it looked as if they were going to overcome their poor start and do it again. They finally had tied the game with 4:30 left to play, had momentum on their side, and it looked like they were going to win.

Until they didn’t.

In retrospect, it was surprising they were there at the end with a chance to win. Kevin Garnett had a bad game, in foul trouble, pushed around much of the night by Pau Gasol of all people. The loss of Kendrick Perkins, out with a bad shoulder, took away a big, physical body. Outside of the Big Three, no other Celtic was in double figures, and if not for the brilliance of Paul Pierce the Celtics would have been long gone from the beginning.

But once again the Lakers showed why they’re such a trick-or-treat team. They are so dependent on Kobe Bryant, and when he’s got it going they can score points like some pinball wizard. That’s the Lakers at their best, for they are a finesse team and Kobe is the ultimate finesse player. They are a team that wants to outscore you, and when you make it difficult for them to do that they struggle.

That’s the simplistic analysis anyway, and for the most part that’s been the basic outline of this series. The Celtics are better defensively, tougher, which is why they figure to win this series, whether it’s tonight, or Game Seven on Thursday.

“We played harder than the Celtics,” Phil Jackson said after Sunday night’s game. “We scrapped it out. We had more possessions and made more shots.”

Sounds simple, right?

It’s not. Playoff basketball is all about bringing energy, certainly, but some teams are more physical by nature. The Lakers are not. Gasol is a European finesse player. As skilled and versatile as former URI star Lamar Odom is, he has never been a physical player. The Pistons they are not.

Still, the other night they took the game to the Celtics in the closing minutes in ways they hadn’t done before, lived to play tonight.

But we aren’t in Kansas anymore and the Lakers aren’t in L.A. anymore either, where celebrities line the court like in the very definition of California Cool.

Asked Sunday night if the Lakers’ style of play in Game Five could lead to a win in Game Six, Kobe said, “Probably not, we’ve got to play better.”

Can they?

The odds say they can’t.

More important, the Celtics aren’t in L.A., anymore either.

They are back in the Garden, where they have lost only once in the playoffs, the place where they’ve been so good all year. They are back in the Garden, where they feed off the crowd and the energy, back in the Garden under those 16 championship banners. Back in the Garden with all the odds in their favor.

Could it be any better than this?

It’s been said that the toughest game to win in any series is the fourth game, but can you ask for anything more than to only have to win one game with two chances at home to do it?

For the Celtics are back home where this amazing story continues, back home where the stage is set for our biggest basketball moment in 22 years, back home where all those old ghosts of the past now smile down on this team that’s come from nowhere in just one year. Back in Boston, where it seems as if this wonderful script is just waiting for the right ending.

breynold@projo.com