It comes after a brilliant display from the Eagles to down the Red Devils 3-1.
The former Tottenham winger opened the scoring in the seventh minute to give the visitors a deserved lead.
And he has revealed the true reason why they tore United apart with such ease.
The victory follows their win over Southampton to mark a fantastic start to the season under Roy Hodgson.
But when asked whether Townsend was surprised by Palace’s start to the season, he told Sky Sports: “No we know we have a good enough squad.
“We added one or two young players and are fully confident.
“With United having their first game here we thought we could catch them cold.
“Once we get ahead we’re a well drilled team and knew we had enough to stay in front. Mentally we knew we had an advantage.
Manchester United are looking to plot their path back to the top. Ole Gunnar Solskjaer has already brought in Donny van de Beek but Jadon Sancho remains Manchester United’s number one target.
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“We knew if we started fast we might catch them cold and then it was a point of seeing out the game plan.”
True to his word, that is exactly how they scored in the opening exchanges.
But it was Palace who pushed for a second and only a brilliant save from Jordan Ayew prevented them doubling the lead before the whistle went for the first half.
They eventually got the second, though it came around in controversial circumstances.
As Ayew flicked a ball up, it stroked Victor Lindelof’s hand and after a lenghty VAR check, Martin Atkinson gave a penalty.
But it did not end there, with Ayew’s effort saved by De Gea.
However, the Spaniard had left his line before the ball had been kicked, meaning the penalty had to be redone much to the fury of United’s players.
This time, Wilfried Zaha stepped up to score past his former team – and he was on hand to grab a brace with a fine drive in the closing minutes.
That came after Donny van de Beek had come on for his debut and scored.