Myles Turner is about to become teammates with Giannis Antetokounmpo, while Damian Lillard has the chance to pick his next spot.

And just like that the first full day of NBA free agency brought big surprises on Tuesday.

Indiana Pacers stalwart Turner agreed to a four-year deal to join the Milwaukee Bucks, who waived the nine-time All-Star in Lillard to make the acquisition happen, according to a person with knowledge of the moves.

Turner is agreeing to a deal that ends with a player option, after spending his first 10 seasons with the Pacers, who went to the NBA Finals this past season.

The remaining $US112.6 million ($A171 million) owed to Lillard will be paid out over the next five seasons via the NBA's stretch provision, according to a person with knowledge of the deal.

ESPN, which first reported the plan by the Pacers and Bucks, said Turner agreed to a contract worth $US107 million.

In both cases, achilles tendon injuries played a role in how things unfolded.

Indiana expect to be without star guard Tyrese Haliburton for the coming season because he ruptured his achilles tendon in Game 7 of the NBA Finals against Oklahoma City while playing through what was diagnosed as a calf strain.

Earlier, Lillard ruptured his achilles tendon playing for Milwaukee in Round 1 against Indiana.

Lillard is likely to miss most, if not all, of the coming season. He will be free to sign with anyone he chooses, and teams could simply sign him now, give him a chance to continue his recovery and do so with hope he is ready to go by the start of the 2026-27 season.

"This is an opportunity for Damian to stay home to continue his rehabilitation, take time to decide where he wants to play next, while still being paid his entire contract," said Lillard's agent, Aaron Goodwin.

Turner has averaged 14.1 points and 6.8 rebounds in his 10 seasons with the Pacers.

Lillard, who turns 35 this month, has averaged 25.1 points and 6.7 assists in 900 regular-season games over 13 seasons - the first 11 with Portland, the past two with Milwaukee.

Meanwhile, Shai Gilgeous-Alexander and Oklahoma City have reportedly agreed on a record-setting four-year, $US285 million extension that would give him the highest single-season average salary in NBA history.

He is coming off a year when he became the fourth player in NBA history to win MVP, Finals MVP and a scoring title and play for a champion in the same season. Others to achieve the feat are Kareem Abdul-Jabbar, Michael Jordan and Shaquille O'Neal.