The 24-year-old Republic of Ireland winger came within inches of shocking world and European champions Spain in New York early on Wednesday morning when he blasted a rising shot towards the Real Madrid goalkeeper's goal with 10 minutes remaining.
The Ireland fans inside the stadium rose to acclaim a famous equaliser, only to see Casillas somehow smuggle the ball away to rob the Sunderland winger of his glory, and McClean said: "I did everything right. He dived before I hit it and there was an element of luck as well as world class."
He added: "It would have been nice to have on the CV - a goal against Spain at Yankee Stadium - but it wasn't to be. But he's not one of the best in the world for nothing, so it just wasn't to be.
"He was like a cat, wasn't he? He dived and somehow - I don't know how - he saved it. But as I say, he's not one of the best in the world for nothing, is he?"
Ireland were trailing 1-0 at the time to substitute Roberto Soldado's 69th-minute strike despite having been on the back foot for much of the game.
They thought they were back in it seconds later when central defender Sean St Ledger stabbed home from close range after Casillas had managed to turn Stephen Kelly's glancing header on to the bar, only for an offside flag to curb their celebrations.
Juan Mata increased their disappointment at the death with an 88th-minute second for the Spaniards, but the Republic at least restored some of the pride they lost when they were trounced 4-0 by the same opposition at last summer's Euro 2012 finals.
McClean said: "We have come on in leaps and bounds from Poland. We have got a relatively young squad now with a mixture of experience in the likes of Robbie (Keane).
"It bodes well for the future."
- Sports & Recreation