The Brazilian tore the Red Devils apart on Monday night, netting twice as Tottenham ran out 3-0 winners over United at Old Trafford.
"Right towards the end of my time at United we were pursuing Lucas Moura, the immensely talented right winger who, at the time, was playing in his native Brazil for Sao Paulo," wrote Sir Alex Ferguson in his book, 'Leading.'
"We offered £24m for him, which was upped to £30million and again to £35million, but Paris Saint-Germain signed him for £45million.
"David Gill and I were just not prepared to go to those sorts of levels."
Moura spent five years in France with PSG before Spurs landed him midway through the 2017/18 campaign.