Berenguer’s agent Juan Oyaga said last month a switch to Napoli was close, but no agreement could be reached with the Partenopei.
Fellow Serie A side Torino have instead snapped up the 22-year-old, who played 29 times in LaLiga last season, scoring once and contributing a team-high six league assists, although Osasuna were relegated after finishing 19th.
“The club wishes to express its gratitude to Alex Berenguer for his behaviour during the negotiations, through which he has sought the best for his future, but with the sensitivity of waiting for the club to receive the most optimal offer for its interests,” a club statement said.
Berenguer – who had a €9million release clause – waived a condition of his contract entitling him to 15 per cent of the transfer fee, while Torino have also agreed to pay Osasuna a further €1.5m if they sell the Pamplona-born player to Basque club Athletic Bilbao.
“I received an offer that I could not refuse,” said Berenguer. “I asked the club to let me go because there are trains that only come once in a lifetime and you have to take them. It’s not a simple decision, but it’s a big opportunity for me.
“I wanted the deal to be beneficial for the club because it gave me everything and I will always be grateful. Osasuna will always be my home and will be in my heart.”