The Thunder star came to Oklahoma City in 2019.
The Thunder's star player scored the decisive baskets deep into double overtime as the defending champions started their championship campaign with a 125-124 win over the Houston Rockets.
The reigning MVP scored a team-high 35 points, featuring two from the free-throw line with just mere seconds remaining in double OT, securing the champions a positive start.
The Rockets' big man top-scored with 39 points and also hit a personal-best five three-pointers.
But Chet Holmgren, who added 28 points of his own, played a major role together with the game's hero.
"Grit and defence," SGA commented of their performance. "We know that when we do it on defence we give ourselves a chance no matter what's going on—shots, misses, fortune or bad luck. We did sufficient defensive work to secure the victory. We're pretty rusty, but it's a positive beginning."
Prior to the tip-off, Oklahoma's championship banner was raised at their arena, while the squad were awarded their championship rings.
The Thunder defeated the Indiana Pacers in last season's championship series. It was their first title since the team moved in 2008 to OKC from Seattle, who had claimed the 1979 title.
Indiana will have the chance to secure some early revenge on this Friday when they host the Thunder, while the Rockets return to action on the same day at the Pistons.
Elsewhere, a massive performance of 43 points, 12 rebounds and nine dimes from the Slovenian star was not enough to prevent his current team the Los Angeles Lakers from falling to a 119-109 loss against the Warriors.
Miami's star scored 31 points and Golden State's sharpshooter added 23 points for the visiting Warriors.
The Lakers were without the league's top scorer LeBron James as he is recovering from sciatica.