Eto'o departed the Camp Nou after scoring 30 LaLiga goals and the opening strike in the 2-0 UEFA Champions League final triumph over Manchester United.
However, Guardiola transfer listed the African superstar in the following season, which led to his Inter move, with Zlatan Ibrahimovic heading in the opposite direction.
Speaking to BeIN Sports, the four-time African Player of the Year revealed his dismay upon finding out he was discarded by the Spanish tactician and claimed it went down as the most historic transfer in football history.
"My lawyer at the time told me that the club had put me up for sale on the transfer market. I said really? He said yes, at Guardiola's request," he said.
"It's clear today, that move, and the opportunity that Pep gave me has gone down in history because it permitted me to be an even bigger part of football history by going to Inter.
"He allowed Inter to strike the best deal in football history."
Eto'o went on to lift second consecutive domestic treble under Jose Mourinho playing a decisive role in the run to lifting a second straight Champions League winners medal.