When Isaiah Thomas caught fire in a seven-game playoff series against Washington last year, he did so with a Lakers legend in his ear.

Thomas was playing for the Boston Celtics at the time, making it all the stranger that Kobe Bryant was giving him constant advice throughout the postseason.

“We’d be on FaceTime watching film together on speakerphone,” Thomas said during his Lakers Voices chat on Tuesday. “He would tell me what he sees, what I can do and what I can do better to be able to get my team a win. That was throughout the whole playoffs.

“That was special to me, because to be able to have Kobe Bryant talk to you and help you out is amazing, especially for me. That was my favorite player growing up.”

Thomas — now playing for the purple and gold — was a big Lakers fan as a kid thanks to his father, James, who is from Inglewood.

So that’s why, a few years ago, Thomas contacted through his people to see if Bryant would be willing to let him pick his brain before a game between the Celtics and Lakers.

Bryant agreed and spent an hour talking with Thomas. Afterward, they kept in touch over text, and Bryant reached out to Thomas when his sister, Chyna, died in a tragic car accident during the opening round of the playoffs.

Through his emotional pain, Thomas continued to play at his MVP-caliber level. When it came to a second-round series with the Wizards, he hit a new level, thanks in part to Bryant’s advice.

“I’m a guy that watches a lot of film … and I thought what I was watching were the right things,” Thomas said. “When we first sat down and watched film last playoffs, he was just going in so much detail of things that I never even looked at on film.”

Bryant advised that Thomas watch film on Stephen Curry, including studying how the Golden State point guard would set screens to open up scoring opportunities for himself and others.

Thomas soared in that series, averaging 27.4 points, 7.1 assists and 3.6 3-pointers.

“It was crazy, because I never even thought about basketball like that,” Thomas said. “And then when I started to think like that, I would see it before it happened in the game and I would think, ‘Damn, Kobe really just told me that last night.’”