The Celtics had far and away the best chance of landing Paul George in a trade from Indiana.

Until they didn’t.

League sources quickly confirmed an ESPN report that the Pacers are trading the All-Star forward to Oklahoma City for Victor Oladipo and Domantas Sabonis. Indiana was under the gun to move George, who had informed the team he was going to opt out of his contract after the coming season and leave as a free agent.

The news hit the Celtics as they were preparing to make their midnight free agent phone calls, and according to sources among those who have dealings with the club, the C’s were stunned.

They had gone hard after George at the February trade deadline, offering this year’s Brooklyn pick (through a swap of first-round positions) that became No. 1 overall. The thinking for the Celts is that they would have a year-plus to convince George to stay in Boston.

In their latest attempts to get George over the last several days, they were unwilling to include next year’s first-round draft pick from Brooklyn or the Lakers 2018

Sacramento 2019 pick they received from Philadelphia as an inducement for moving down from No. 1 to 3 in this year’s draft. The Celtic also did not want to part with their top picks from the last two years, Jaylen Brown and Jayson Tatum.

But sources confirmed the C’s were more than ready to give the Pacers players with better contracts and multiple draft picks other than the ones mentioned in the previous paragraph. The best offer was two starters — almost certainly Jae Crowder and Avery Bradley — and three first-round draft picks.

Oladipo is scheduled to make a guaranteed $21 million in each of the next four years. Sabonis, who averaged 5.9 points and 3.6 rebounds in 20.1 minutes in his first season, is still obviously on his rookie contract.

One league executive told the Herald earlier yesterday that the Pacers might be looking to get a third team involved in a trade, adding, “but I still don’t think Indiana can get the combination of young players who can help them now and maybe picks from anyone other than Boston.”

Reached last night, that same source said, “I can see what OKC is doing, but I really can’t believe this from Indiana’s standpoint. There’s no way you can’t get more than that. And you’ve got to get at least something in the way of draft picks.”

A Western Conference source agreed with the Celtics’ decision to hold back the Nets and Lakers/Sacramento picks as well as Brown and Tatum.

“I can understand what Boston’s thinking on that,” he said. “If you’re only guaranteed to have George for one year, you have to ask yourself whether he’s going to be able to win it all for you with whatever else you’re able to put together. And with Golden State sitting there, how realistic is that? Not very.”

The Thunder clearly aren’t as concerned with losing George next summer. The club is trying to show commitment to Russell Westbrook, who can also opt out next year and who they’re trying to woo with a longer term deal. Even if George walks, they will be able to start off a rebuild with a lot of money to spend in a free agent market where a number of teams have been eliminated from the party because of what they’re spending last year and this, when the new television contracts kicked in and raised the salary cap dramatically.

With the George trade having shaken the league, the Celtics were said to be getting quickly back to the business at hand, which was making a midnight phone call to profess their affection for Gordon Hayward at the start of the free agent negotiating period.

They will meet with Hayward here tomorrow.

The Celts have been aware for some time now that Hayward would be opening to at least hearing their presentation, but, with others in the running, they can have no strong confidence that he will choose them. The All-Star will also be meeting with Miami and incumbent Utah.

There really isn’t much of a Plan B for the Celtics in free agency. They did have some interest in Blake Griffin, but he is going to remain with the Clippers.

They may look elsewhere in the market, with long-time Celt target Danilo Gallinari worth a look if the price is right. But if the C’s cannot attract Hayward, it may be of little sense to try to sign a player of lesser value. The best course of action then would seem to be to give those wing minutes to Brown and Tatum with the hope/expectation they could develop into the kind of players you’re throwing max millions at today.