The Portuguese winger was controversially sent off vs. Real Madrid for a high tackle on Alvaro Arbeloa with Man Utd 2-1 up on aggregate, and Giggs was incredulous at the decision.
The Portuguese winger was shown a straight red by referee Cuneyt Cakir after a high challenge on Alvaro Arbeloa with the Red Devils 1-0 up on the night, but goals from Luka Modric and Cristiano Ronaldo following the sending off sent Los Blancos through 3-2 on aggregate.
Giggs, who made his 1,000th career appearance in the defeat at Old Trafford says he turning the page to focus on Sunday's FA Cup quarterfinal against Chelsea but expressed his disbelief in the moment.
"I'd initially gone over to tell [Cakir] that Nani was looking at the ball," Giggs told the Daily Mail. "I've gone back to my position on the edge of the box, because they've got a free kick. I was actually looking at the referee when he did it [showed the red card]. I've never, ever experienced a shock like it on a football pitch because I just didn't expect it. And I've never seen a stadium in shock like that.
"I probably haven't felt that disappointed for a long, long time. The manager always says about games in Europe: 'Be careful because the roof can fall in.' And it did, but not in a way in which you can really blame the players, tactically or some of the performances. It was silent and everyone was gutted. It was shock really."
With a crucial FA Cup quarterfinal looming against Chelsea, Giggs has been helping some of the younger squad members through the pain of the Madrid defeat and insists the Red Devils can move on quickly from the result.
"As an experienced player, you've got something to fall back on," Giggs said. "You've known this before. A lot of the younger players may not have, but in five days you've got to quickly turn it around to another massive game, a cup game [against Chelsea] when anything could happen.
"For young players, there might be that little doubt in their mind that we've gone out of the Champions League: 'Did I play well or not?' But there wasn't one lad really that didn't play well. It was a good performance. Everything was spot-on, up until the sending-off of Nani, obviously. So there's a lot to be proud of."