John Stamos said his pal and mentor Mike Love is currently facing “serious” health challenges.

“I’m boarding a plane to Nashville to play with the Beach Boys at the Ryman Auditorium, struggling to put my feelings into words,” the “Full House” actor wrote on Instagram Sunday alongside two photos of him with the Beach Boys frontman.

“My beloved friend, father figure, musical hero and mentor, Mike Love, is facing serious health challenges,” Stamos added.

“We hope he’ll be doing what he loves for years to come, but we don’t know what the future holds. We have tonight.”

The “ER” alum, 63, said Love, 85, is a “fighter” and though doctors urged him to “focus on his health,” he “insists on being on stage.”

“He says he needs his band, the audience, his friends and drummer surrounding him to lift him up,” he penned.

“I’ve played with Mike for 41 years. I never imagined how deeply it would affect me to see someone larger than life face something so human and fragile,” Stamos, who has been performing various shows with the Beach Boys since the ’80s, said.

“The Mike Love we see tonight may not be exactly the Mike we’ve always known. But he’s still every bit the Mike we love.”

Stamos then wrote that the “hardest part of loving” someone is “becoming so accustomed to the miracle of having them there that you forget it’s a miracle at all.”

“I want to cherish every second without feeling those seconds slipping away,” he added.

“That’s what I’m giving him. We don’t know what tomorrow brings. But we have tonight,” Stamos concluded.

Page Six has reached out to Love’s rep for comment but did not immediately hear back.

Stamos’ message comes after a video of him performing with Love went viral on X.

In the clip, the “Good Vibrations” singer was seated onstage as he mimicked some of the dance moves the “Fuller House” alum did.

Over the summer, Love publicly discussed health and personal challenges, including the death of his sister and his recovery from bronchitis and COVID-19, which he said had taken an “emotional and physical toll” on him.

Last month, the Beach Boys abruptly canceled several concerts just one day before they were scheduled to return to the road from a two-month break.