Sporting Lisbon vice-president Francisco Salgado Zenha claims Manchester United paid over the odds for Bruno Fernandes.
The Portuguese giants were locked in a lengthy transfer dispute with the Red Devils and were at loggerheads over the price tag for the playmaker.
But United eventually gave in and agreed to pay Sporting a fee which could rise to £67.8million with add-ons to land their captain just before deadline day.
After a long-running and drawn out transfer saga, Zenha is under no doubts his side were the ones to win the negotations.
They are believed to have netted around £46million in advance with scope for more than £20m more in add-ons - and he says they held their nerve after United wrongly believed they would cave.
"I realised in the negotiations that Manchester United was convinced that we were going to give in and that for 50 million euros he was doing the deal. Well, they ended up paying 65 million," Zenha said, via Record.
"They were wrong and ended up paying what we wanted. We went to get 20 million more than if we had sold four months ago."
Fernandes made his debut just two days after completing his move, playing 90 minutes in a goalless draw with Wolves.
The playmaker will again feature as they head to Chelsea on Monday night - and first-team coach Michael Carrick this week discussed how he has instantly impressed in United training.
"Yeah, he feels at home in this weather!" Carrick said at their warm-weather training camp in Marbella.
"It's what he's used to, but yeah he's settled in really well. He's an intelligent, smart lad and speaks great English so it's been pretty seamless so far.
"There's plenty of Portuguese-speaking (players) anyway. But he's fine, he's settled in really well and he'll just be looking to get games under his belt now and improve as time goes on.
"There's so much to talk about, really. I think the main thing is his composure and quality on the ball. He sees a pass, he looks to play the pass and he can score goals.
"But it's more that composure, understanding of the game and game intelligence really that I like the most about him, and I'm sure we'll see plenty of that."
