The defender thanked the Barca skipper, who has announced his intention to leave Camp Nou in the summer, saying the veteran will be irreplaceable.
The 35-year-old has been a key part of the Catalans defense for more than a decade, but on Tuesday announced his intention to leave the reigning La Liga champions this summer when his contract ends.
Pique, who returned to the Catalans from Manchester United in 2008, penned a tribute letter in response to his centre-back partner's upcoming exit and says he cannot fathom the possibility that Barca will find an equal replacement.
"The day has come. You're going," he wrote in a note for Puyol written publicly on his official Facebook page. "It might be the way of life, but it is impossible to imagine a Barca without you. When I look back and remember [victories in] Paris or Rome, the first image that come to my mind is you lifting the European Cup. At Wembley, you gave the honour to Eric Abidal, a gesture that makes you even greater.
"My generation and those that come after us don't know a Barca without Puyol in the back four, with the armband and the No. 5 on the back. I guess nothing will be the same," the note continued. "I met you almost six years ago. You were the captain and the symbol of the team and I was a youngster eager to conquer the world.
"From the first day we had a great relationship, both on and off the pitch. At your side, I felt protected, I knew that if I failed one day, you would be there to save me. You are my guardian angel. I want you to know that I will miss our chats in the dressing-room, your advice and, above all, your scolding on the pitch. You are unique and one of a kind. I have to laugh when they talk about signing the new Puyol - they can keep on looking, because they never will find him."