SAN ANTONIO ? If the NBA wants to take the retro craze to the next level, they’ll let the Spurs and Nets play with a red, white and blue ball.

The NBA Finals don’t begin until Wednesday night, providing plenty of time to look back on what happened long ago.

New Jersey and San Antonio weren’t even part of the NBA three decades ago. They were in the ABA, which used that tri-colored ball.

Although the Nets and Spurs have been in the finals before, this will be the first time that two former ABA teams will meet in the NBA Finals. The Spurs defeated the New York Knicks in 1999; the Nets were swept by the Los Angeles Lakers a year ago.

The last time the teams played each other in the postseason was 1976, when Julius Erving’s Nets defeated George Gervin’s Spurs in seven games in the ABA semifinals. Game 7 was played April 24, 1976.

The next day, Tim Duncan was born.

The Nets went on to defeat the Denver Nuggets to win the title that season, which was the last for the ABA. The Nets, Spurs, Nuggets and Indiana Pacers were absorbed into the NBA the following summer.

Michael Goldberg, director of the National Basketball Coaches Assn., was the lead attorney for ABA commissioner Dave DeBusschere during those merger talks.

He recalled that the ABA owners went to the NBA’s league meetings in Hyannis, Mass., expecting to stay for one day but ending up staying for four. As part of the merger, two ABA franchises — the Kentucky Colonels and the Spirits of St. Louis — were dissolved.

“After a full night of negotiations we had the press conference, and then we just sort of looked at each other weary-eyed and walked away. There was no champagne, no violins, no big embraces. We were pooped and exhausted — almost shell-shocked that we got into the NBA,” Goldberg said Friday.

Before the Spurs even were the Spurs, they were known as the Dallas Chaparrals — entering the ABA as an expansion franchise in 1967. One of their first draft picks was Pat Riley.

The Chaparrals played their final game March 26, 1973, a 122-120 victory over the Carolina Cougars in front of a paid crowd of 134.

A group led by San Antonio businessmen Angelo Drossos and Red McCombs leased the Chaparrals for $1 for the 1973-74 season, then purchased the franchise for $725,000 from a group headed by future Dallas mayor Bob Folsom.

The Spurs made the biggest acquisition in franchise history on Jan. 30, 1974, purchasing Gervin from the Virginia Squires for $300,000.

The Nets fleeced the Squires, too, a year earlier when they sent George Carter, the rights to Kermit Washington and cash to Virginia for Erving, who was the MVP of the ABA in that league’s final three seasons.

But the Nets, needing cash to pay indemnity fees to the New York Knicks, sold Erving to the Philadelphia 76ers following the merger.