The Boston Celtics’ season ended on a bittersweet note Thursday night. But before C’s fans start feeling too down, here’s a friendly reminder: The fun begins now.

With the Celtics’ season officially over after the Atlanta Hawks eliminated them in the first round of the NBA playoffs, the focus shifts to the offseason, and the host of free agents that president of basketball operations Danny Ainge has the assets to chase. The prize of the free-agent pool is Oklahoma City Thunder forward Kevin Durant, and it appears the C’s already have him in their sights.

The Celtics will be “aggressive in free agency” this offseason, and “that means a run at Kevin Durant,” team sources told The Vertical’s Chris Mannix.

“The Celtics believe Durant will meet with them this summer,” Mannix wrote Friday. “But they know that meeting won’t accomplish much unless there are significant moves leading into it.”

The Durant-to-Boston buzz has persisted ever since the All-Star forward complimented the city during the Thunder’s visit in March. The Celtics even have been reported as a “dark horse” candidate to land the 27-year-old superstar.

But Mannix cautioned that Boston will face stiff competition, both from Western Conference titans in the Golden State Warriors and San Antonio Spurs and from the Thunder, all of whom are in better position than the Celtics to help Durant win a ring.

“Boston needs a deal for (Chicago Bulls guard) Jimmy Butler, a commitment from (Atlanta Hawks forward) Al Horford, a carrot to dangle in front of Durant to persuade him that relocating east is the smart play,” Mannix writes.

Durant coming to Boston might be a long shot, but it appears Ainge and Co. certainly will try.

Thumbnail photo via Mark L. Baer/USA TODAY Sports Images

Thumbnail photo via Oklahoma City Thunder forward Kevin Durant (35) claps during the first half of a game against the Boston Celtics at TD Garden.