The Serie A side admit it may have been better to stop the Chile international from joining the Spanish and European champions
The Spanish champions paid an initial €26m which could total €37.5m depending on variables which are performance-related.
And while the Italians cashed in, Larini feels it would have been better to hold onto the player for longer.
"Initially we did not want to sell our best players because we knew we would be playing in the Champions League," Larini is quoted as saying in La Repubblica.
"We had really hoped to keep Sanchez for another year, but then with the passing of time there was pressure from Manchester City, Manchester United, Barcelona, Inter and Juventus and so in the end we had to give up and sell."
Udinese were dumped out of the Champions League after losing to Arsenal in the qualification play-offs for the group stages, while Sanchez has started his career in La Liga in style following Barcelona's 5-0 win over Villarreal last week.