Shai Gilgeous-Alexander scored a career-high 55 points to lead the Oklahoma City Thunder to a double-overtime victory against the Indiana Pacers in a rematch of last season's NBA Finals.

The reigning NBA Most Valuable Player added eight rebounds and five assists as the defending champions claimed a 141-135 win.

It came just hours after the league was rocked by an FBI investigation into illegal sports betting and an illegal poker ring tied to organised crime.

Gilgeous-Alexander had scored the winning points in a double-overtime win against the Houston Rockets in the Thunder's season-opener on Wednesday.

Once again the Canadian guard proved crucial, netting nine points in the second overtime as he beat his previous career-best of 54 points.

"This team has two great qualities," Gilgeous-Alexander said.

"It knows how to stay in the moment and it understands that the beginning of the season is just as important as the end of the season."

The Thunder became the first team in NBA history to go into double overtime in their first two games of a campaign.

Indiana have been without star guard Tyrese Haliburton, who tore his Achilles tendon in June, while they suffered another injury blow on Thursday when they lost guard Andrew Nembhard to a shoulder injury in the second quarter.

Elsewhere on Thursday, Stephen Curry scored 42 points to lead Golden State Warriors to a 137-131 win in overtime against the Denver Nuggets.