For John Stamos, losing friend Bob Saget in January was "heartbreaking" for more than the obvious reason.

"It was so heartbreaking to see [that] he didn't know how loved he was," Stamos told ABC Audio. "I guarantee it. And to... to think that he didn't feel that. It really hurts me."

MORE: John Stamos says losing Bob Saget helped inspire him to write his memoir 'If You Would Have Told Me'

The actor said he was "grateful" he got to channel his grief into the upcoming season of the Disney+ show "Big Shot," debuting Oct. 12. He helped craft a storyline in which his coach character, Marvyn Korn, loses a "close friend and mentor."

"He sees this outpouring of love for his friend, and he goes, 'Where's my legacy? What am I leaving behind?' " Stamos said. "Because people go, and then they never -- they don't get to hear how much everybody loved them."

Marvyn's players and his daughter get to tell him precisely that in the show, he said.

PHOTO: Bob Saget and John Stamos at the Beverly Wilshire Four Seasons Hotel on April 25, 2019 in Beverly Hills, Calif.
Michael Tullberg/Getty Images, FILE
Bob Saget and John Stamos at the Beverly Wilshire Four Seasons Hotel on April 25, 2019 in Beverly Hills, Calif.

"That's a lesson, too, from Bob," Stamos added. "Like, he left nothing on the table. You just go tell people that ... when you get a chance, that you love them, that you care about them, that you're proud of them -- whatever it may be, because tomorrow's never promised."

Stamos recalled how Saget always sent sincere texts to those he loved, sometimes for no reason at all.

MORE: ‘Full House’ cast pays tribute to Bob Saget: ‘We grieve as a family’

"Long texts, and there were a lot of dirty words mixed into the love and kindness. If we're real quiet right now, we can hear him complaining in heaven that I'm not talking about him enough today," he said.

"I miss him, you know," he added. "I miss him."