Barbra Streisand mourned the loss of her longtime manager, Marty Erlichman, who died at 97.

Erlichman, who discovered the entertainment icon and guided her career for more than six decades, died Saturday (Oct. 31) from age-related causes, per PEOPLE.

Streisand paid tribute to Erlichman on Instagram Sunday (Nov. 1), sharing a photo of the pair and reflecting on their lasting bond.

"Although Marty lived a long and full life, nothing can prepare you for the reality of losing someone so dear," the legendary musician wrote. "I truly thought he would live forever. In my eyes, he was simply indestructible-always by my side, through everything."

She added that the two "never even had a contract" and said she would be "forever grateful for his friendship, loyalty, and unwavering support."

Erlichman helped guide every aspect of Streisand's career, from recording and film deals to concerts and tours. He also executive produced her 1994 HBO special Barbra: The Concert, earning an Emmy and a Peabody Award.

He is survived by his wife of 52 years, Miko Mayama Erlichman, their son, J.J., and four grandchildren.