In sudden twist, Al Horford tells Celtics he is likely to accept an offer from another team

Al Horford, 33, has made it clear he would like to contend for a title.Barry Chin/Globe Staff/Globe Staff

The Celtics’ strange and uneasy summer has taken perhaps its most surprising twist. According to league sources, forward Al Horford in the last few days informed the Celtics he is likely to accept an offer from another team after free agency begins on June 30.

It would be a crushing blow for Boston, which already was unable to acquire Anthony Davis from the Pelicans and is prepared for Kyrie Irving’s departure, too.

Horford declined his $30.1 million player option with the Celtics for next season, making him an unrestricted free agent. It was widely believed he did so with the intention of re-signing with the Celtics on a longer-term deal at a lower average salary.

On June 5, Celtics president of basketball operations Danny Ainge was asked about the possibility of restructuring Horford’s deal this summer.

“That’s one of the priorities on our list,” he said then.

But now, it appears he has his sights set elsewhere. Free agency does not begin for two more weeks, so the timing of Horford’s news is certainly unusual. Nevertheless, sources said, as the Celtics dive into preparations for Thursday night’s draft, they are doing so with the belief that Horford will no longer be part of their future. Given the timing, however, a league source said that the team remains hopeful it can still come to an agreement with Horford before it is too late, although few know if that time already has passed.

When Horford signed a four-year, $113 million contract with the Celtics in 2016, it was one of the biggest free agent coups in the franchise’s history. Horford, who is now 33, said then he decided to come to Boston in large part because the team was on a path to championship contention.

The Celtics reached the Eastern Conference finals in each of Horford’s first two seasons, including a stirring run in 2017-18 when stars Kyrie Irving and Gordon Hayward were out with injuries.

When Hayward and Irving returned at the start of last season, expectations were massive. But the team floundered to a fourth-place finish in the Eastern Conference and was then walloped by the Bucks in five games in the conference semifinals.

After that Game 5 loss, Horford, in retrospect, was somewhat cryptic about his future. He said he enjoyed being in Boston, but had not stopped to think about his future.

“Just have to wait and see what we’re going to do as a team,” Horford said. “And the steps that the management is going to do moving forward.”

When Horford was asked about the roster for next season, he said: “You know what, I’m not really sure. That’s something that management is going to have to figure out. They’re going to have to see what the future looks like for us.”

Since then, of course, Boston swung and missed on Davis, and Irving’s departure became increasingly imminent. And Horford’s longtime dream of winning an NBA title became more cloudy.

Horford always seemed to have a great appreciation for the Celtics’ culture, coaching staff and fan base, and at this point in his career there was a thought he may value those things more than he did when he signed with Boston three years ago. But now, it appears that his championship desires are still very strong.

One league source said Horford’s potential departure would not affect the team’s draft preparations this week. Boston holds the 14th, 20th, 22nd and 51st overall selections in Thursday’s draft.