The Argentine is set to sign for the champions of his homeland until the end of the season after becoming dissatisfied with life in La Liga in recent months
The Argentine moved to Mestalla from Real Madrid at the start of the season, but has been rumoured to be unhappy since the dismissal of Mauricio Pellegrino as coach of the club.
He had been linked with a move to Boca Juniors, but Velez have won the race for his signature despite interest from Brazil.
"It took me by surprise," he told Rock & Pop. "My plan was to stay at Valencia. I'm in Argentina for six months, then I will return to Valencia.
"I was not hoping to leave Valencia. [Ernesto] Valverde told me that he would not consider me. I need to play to have the opportunity to be in the team.
"Valencia told me they never got an offer from Boca for me. I got nothing official from them. Since I went to Real Madrid, Boca have said every year that they love. You have to wonder if it's true.
"Boca is my home. I grew up there from when I was little. I spoke to [Argentina coach Alejandro] Sabella before signing for Velez. Personally, and sportingly, Velez was the best option."
The 26-year-old first moved from Argentina to Spain in 2007 and has also enjoyed a loan spell at Roma.