The Real Madrid legend has hailed the Barcelona captain's influence and loyalty and believes he will prove hard to replace at Camp Nou
The Barcelona skipper announced his intention to leave Camp Nou at the end of the season earlier this year, leaving the Blaugrana in dire need of defensive reinforcements.
And the 45-year-old believes Puyol will be nearly impossible to replace due to his influential nature and the Catalans' style of play.
"Puyol is a great, an example for everyone for his honesty and his loyalty," he is quoted as saying by AS.
"He will go down as one of the best three centre-backs in the history of Spain. I have the upmost respect for him. He'll go down in history.
"It's always difficult to replace a player like Puyol. Barca will try and search for a replacement for Puyol at home. It's not that easy to find good centre-backs who can adapt to Barca's game, when you have to defend high up."
Hierro also claimed that Barcelona's era of dominance is now coming to an end, insisting it would be "impossible" to maintain the standards set under Pep Guardiola forever.
"There comes a time when success becomes an obligation. When you are in a winning cycle, everything is a requirement.
"Everyone thinks you can play at the same level as Pep Guardiola's Barca forever, but I think that's impssible."