Whoever coined the phrase “the rich get richer” could have been talking about the NBA.

Just look at what the top five teams in the West have done:

The Spurs added two new starters and a couple of key reserves to a team that won the title.

The Lakers added a pair of future Hall of Famers to play alongside Kobe Bryant and Shaquille O’Neal.

The Mavericks brought in a pair of 20-point scorers, the Timberwolves surrounded Kevin Garnett with plenty of new talent, and the Kings acquired an All-Star center.

“The top teams are still the top teams — San Antonio, L.A., Dallas, Minnesota’s real good, Portland’s good, Sacramento,” new Houston Rockets coach Jeff Van Gundy said. “If you start naming them, and you’re not one of those coaches, you start getting scared because you have to play them all four times.”

The West is so good that the ninth-, 10th- and 11th-best teams in the conference could be playoff-caliber teams in the East. Only one Eastern Conference team, the Detroit Pistons, won 50 games last season, whereas the West had six members of the 50-win club.

And while many of the top teams in the West improved by adding better players, their counterparts in the East often made their biggest changes at the top.

Of the eight Eastern teams that went to the playoffs, five — Detroit, Indiana, Milwaukee, New Orleans and Philadelphia — changed head coaches.

The Cavaliers, Clippers, Wizards, Rockets and Raptors also changed head coaches in one of the most turbulent offseasons ever.

Of course, the summer’s biggest offcourt news was the rape allegation against Bryant, one of the most visible superstars of the post-Michael Jordan era. Bryant, facing up to life in prison if convicted, is trying to proceed with his basketball career when not otherwise required to be in a Colorado courtroom.

The NBA begins its 57th season today, with the Lakers headlining opening night.

Their first opponent will be the reloaded Dallas Mavericks, the league’s highest-scoring team last season even before they brought in Antawn Jamison and Antoine Walker.

If not for a knee injury to Dirk Nowitzki, the Mavs might have made it to the NBA Finals last season. But that didn’t stop them from pulling off a pair of blockbuster deals without having to split up their core of Nowitzki, Steve Nash and Michael Finley.

On paper, it’s debatable whether the Lakers or Timberwolves improved the most.

Los Angeles, ousted from the second round of the playoffs in six games by the Spurs, signed free agents Malone and Payton to try to get them their first championship rings and return the title to Los Angeles for the fourth time in five years.

If he wins another championship, Phil Jackson will break a tie with Red Auerbach for most titles as a coach (nine).

“We may struggle early,” said Jackson, whose team started last season 11-19 before winning 39 of its final 52 games. “We’ve got a much tougher start this year than we did last year. I think our opponents are more high-quality opponents.”

The Kings-Lakers rivalry has been the NBA’s best during the past few seasons, and a new twist has been added through Sacramento’s acquisition of center Brad Miller — an All-Star with the Indiana Pacers last season.

It was January 2002 that O’Neal threw a roundhouse punch at Miller — then with the Bulls — that fortunately missed its intended target. Miller and O’Neal have faced each other just once since then, but they’ll now hook up four times a year.

Wait a minute, what about the East?

Well, the region that produced the utterly unwatchable Pistons-Nets conference finals has undergone changes, too.

Perhaps the biggest change is the addition of Alonzo Mourning to New Jersey, the East’s representative in the past two NBA Finals.

Though they did not improve their biggest weakness — outside shooting — the Nets did add a seven-time All-Star to a lineup that already includes Jason Kidd, Kenyon Martin and Richard Jefferson.

Detroit, Indiana and Philadelphia changed their coaches, and the Boston Celtics traded away their second-leading scorer.