With hours to spare before the start of the N.B.A.’s free agency period, the Oklahoma City Thunder engineered a blockbuster deal on Friday night by acquiring forward Paul George from the Indiana Pacers in a trade, according to a person with direct knowledge of the deal who requested anonymity because it had not yet been announced.

George, a three-time All-Star who had spent his seven-year career with the Pacers, will now form one of the league’s more intriguing tandems alongside Russell Westbrook, the league’s most valuable player, in Oklahoma City. The deal, which was first reported by ESPN, was also a convenient way for the Thunder to bolster their case that Westbrook ought to re-sign with the team. They were prepared to offer him a long-term extension at 12:01 a.m. Saturday, when free agency began.

George, who averaged 23.7 points and 6.6 rebounds a game last season, had recently informed the Pacers that he intended to leave the team once he became a free agent next summer. Rather than allow the remaining year on his contract play out, the Pacers pursued a trade.

In exchange for George, the Thunder shipped Victor Oladipo, their starting shooting guard, and Domantas Sabonis, a 21-year-old power forward, to the Pacers, who, like many other teams around the league, are in full rebuild mode.