Parma President Tommaso Ghirardi says he should have done more to keep Giuseppe Rossi at the club in the summer of 2007.
Rossi spent a successful six-month loan spell at the Tardini when his nine goals in 19 games helped the club survive the drop.
Parma made a bid to sign him outright, but Manchester United opted to sell him to Spanish side Villarreal instead.
“I regret letting Rossi leave,” Ghirardi told Sky Sport Italia. “Five years ago I should have offered United more money to convince them to sell to me.”
Rossi, an Italian international, is currently out injured after snapping knee ligaments for the second time within the last 12 months.
Ghirardi also spoke about the futures of boss Roberto Donadoni and Sebastian Giovinco, the forward who is co-owned with Juventus.
“I’ve had lunch with Donadoni and he’s told me that he wants to stay. We’ll keep a tight grip on him for now, but it is clear that a big club will arrive one day.
“Giovinco? He could remain unless a really top club comes after him. We’ll meet with Juve soon. If they want to keep him then a simple chat will be enough. The problem will be if they want to sell him on…”