United Kingdom, Oct. 12 -- The Beach Boys' Mike Love is "facing serious health challenges", according to John Stamos.

Ahead of their joint performance at the Ryman Auditorium in Nashville, Tennessee, on Sunday (11.l0.26), the 63-year-old actor took to Instagram to pay tribute to the 85-year-old founding member of the legendary rock band, who "insists on being on stage" despite his unknown health battle.

John shared two pictures of himself and Mike, with the caption: "I'm boarding a plane to Nashville to play with the Beach Boys at the Ryman Auditorium, struggling to put my feelings into words.

"My beloved friend, father figure, musical hero and mentor, Mike Love, is facing serious health challenges. We hope he'll be doing what he loves...