The 24-year-old was surplus to requirements with the Catalan giants, but was hesitant about where to take the next step of his career.
He secured a move to Leeds in July for £12.8 million, and admits Orta played a big role in the transfer.
Firpo told Sky Sports: "I never want to forget Victor (Orta).
"Victor comes to me and shows me the project of the team, of the club. I think the first time I spoke with him, I had a clear decision."
He added on pre-season and his first action as a Leeds player: "I've found it good. It's a little bit hard, really physical, doing a lot of sessions of training, but good.
"All the teammates gave me a warm welcome."
Speaking about coach Marcelo Bielsa, Firpo said: "He wants players that press high, one v ones on the pitch, with long distance, I think this is my style of football."
"He's the best, he's amazing. What he can do in the game, in training, was really amazing. For me, he's the best in history."
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