Bobby Marks analyzes the Lakers' addition of Danny Green after losing out on Kawhi Leonard and looks at other free agents they could add to their roster. (1:48)

As fears mounted that the Los Angeles Lakers had pushed to the cusp of creating an unprecedented Big Three, the LA Clippers made a blockbuster trade for Oklahoma City's Paul George -- and cleared the path for free-agent Kawhi Leonard to sign a four-year, $141 million contract with the Clippers, league sources told ESPN.

The Clippers became the last line of defense for the balance of power in the NBA -- never mind the franchise's own future. The Clippers had come to believe that, without a deal for George, Leonard was prepared to sign with the Lakers and create a Staples Center partnership with LeBron James and Anthony Davis, sources said.

Had Leonard joined the Lakers, they would have been overwhelming title favorites, and it perhaps would have thrust the Clippers back into the franchise's dark ages. Now the Clippers are in Western Conference contention, shoulder-to-shoulder with the Lakers -- as well as the Denver Nuggets, Houston Rockets, Portland Trail Blazers and Utah Jazz.

George and Leonard wanted to play together, and George and his agent, CAA's Aaron Mintz, approached Thunder general manager Sam Presti in recent days and requested a trade, league sources said. Leonard's message to Clippers owner Steve Ballmer and president of basketball operations Lawrence Frank was essentially this: Get George, and you'll get me.

Before free agency started, the Clippers knew they needed a second star to lure Leonard but had no idea whom he wanted. The Clippers inquired on deals for Washington's Bradley Beal and New Orleans' Jrue Holiday, but those guards weren't available in trades. Eventually, Leonard made his intentions known to the Clippers: Paul George.

To Leonard, the cost was immaterial. He wanted to walk into a championship contender and believed George represented the co-star he needed to combat James and Davis, sources said. Leonard wanted to play for Doc Rivers, a coach with whom he could feel a kinship he felt was similar to his relationship with Toronto Raptors president Masai Ujiri, sources said.

In the end, Presti made the best of an impossible situation: Despite two years left on George's deal, he didn't want a trade demand hanging over his franchise. Still, he'd never have more leverage to trade George than he did late Friday night, when there were no limits to the Clippers' desperation to land George and Leonard in one dramatic swoop.

In a wild night of negotiations, Presti leveraged the Clippers and Raptors off each other, preying on the uncertainties of what the other might be willing to give Oklahoma City for the chance to secure Leonard and George -- and perhaps the inside track on a championship.

Clippers leadership -- Ballmer, Frank and general manager Michael Winger -- harbored fears that Presti was close to striking a deal with Toronto that would have delivered George to the NBA champions, sources said.

Had Presti been able to strike a deal for George with the Raptors -- and Leonard was willing to stay -- George was believed to be willing to join the Raptors too, sources said. Presti had been willing to pursue a package of Russell Westbrook and George to the Raptors, but no talks ever gained traction, sources said. Ujiri and Raptors GM Bobby Webster had no ability, nor inclination, to counter the Clippers' offer with a multitude of first-round picks into the middle of next decade, league sources said.

The Raptors could have been looking at adding Westbrook, with four years and $171 million left on his deal, and George to a team that Leonard still might have parted ways with. Toronto extended itself as far as it could for Leonard, but Ujiri could never be sure that the Thunder even wanted to do a deal with them -- and perhaps were just using the Raptors to squeeze more out of the Clippers.

play 1:48 How the Lakers can build their roster after missing on Kawhi Bobby Marks analyzes the Lakers' addition of Danny Green after losing out on Kawhi Leonard and looks at other free agents they could add to their roster.

Ujiri had delivered Leonard everything he wanted in a franchise: leadership, trust, championship talent and a medical partnership that preserved and prepared his body. What Ujiri couldn't give Leonard was out of his control: geography, weather and a chance to return to his Southern California roots.

In the end, the Clippers' reservoir of draft picks and young players -- cultivated in the Blake Griffin trade and built on in the flipping of Tobias Harris to Philadelphia -- gave the Thunder a return that the Raptors couldn't match in trade talks, league sources said.

Toronto's pressure was unmistakable: Allow George to get traded to the Clippers and risk Leonard walking into Staples Center arm-and-arm with George to take on James and Davis. This was a high-stakes game playing out across the league Friday night, with the future balance of power hanging.

From the time that Leonard demanded his trade in San Antonio in 2018, the Clippers believed that they had to get him. Here was a top-five player with Southern California roots whose personality maybe didn't fit with the bright lights and scrutiny that comes with life as a Laker. The Clippers withstood several significant obstacles on the way to a free-agent commitment, including Leonard's title with the Raptors and the Lakers' acquisition of Davis.

When it was time to make a decision on sacrificing the franchise's long-term future with a historic haul of draft picks, Ballmer felt he had no choice. Leonard wanted George, and the Clippers paid an unprecedented price in assets. In the minds of the Clippers' decision makers, they were delivering a massive return of assets to Oklahoma City for George and Leonard. Without George, they were losing Leonard to the Lakers, sources said.

Now Staples Center is the NBA's epicenter, and the Clippers can walk Leonard and George into downtown Los Angeles to stand shoulder to shoulder with James and Davis. The wildest story on the wildest night of free agency.