Giggs was less than impressed with his side's performance against the 2010 South Africa World Cup champions in Cardiff.
A brace from Paco Alcácer and goals from Sergio Ramos and Marc Barta was enough to brush aside Giggs' Wales, who lacked the presence of talisman Gareth Bale.
Sam Vokes scored a late consolation for the hosts but Giggs did not see too many positives in the performance.
"We came up against a very good team," he told 'Sky Sports' after the game.
"They are comfortable on the ball and when they lost it they got it back quickly - all the things we knew.
"The disappointing thing for me was not doing the basics. In football you have to do the basics right, even if you come up against an average team. But when you come up against a really good team and don't do the basics right, you're in trouble.
"There was so many mistakes - we conceded some poor goals. To concede that early against this team so early, you're up against it and you have to chase."
Giggs has also confirmed that Bale is "very unlikely" to be fit enough to face the Republic of Ireland.
"That's the good thing about football, you've always got the next game," he said looking ahead to Tuesday's Nations League clash.
"In the last camp we lost to Denmark and you have to wait a month. This time we got beat well in the first game and now we have to react. It will be another tough game but we will be better," Giggs added.