The World Champions recorded a 43-17 win in the first Test in Bloemfontein as the Six Nations champions endured a disappointing start to their tour.
But De Villiers revealed he had watched the video of that game and felt the scoreline was harsh on his side's opponents.
"We're lucky, that score flatters us. Wales were better than that score and they are a better side than what they played like on Saturday," De Villiers said.
"Perhaps they were a little over-confident after winning the Six Nations. But they'll be back. We know they're a good team and that (Warren) Gatland is one of the best coaches around and also that he has been planning for the second Test since Saturday."
De Villiers said his side still had much work to do, hinting he wasn't happy with the scrums and would want his side to gel a bit more under his tutelage.
"Coaches are bad people," said De Villiers. "They are never happy. I'm pleased that we won by such a big margin, but I know we have a lot to work on.
"We will be concentrating on the scrum and kick-offs this week. I'd like the players to develop some continuity, so there should only be one or two changes.
"We weren't adventurous at all, but we said we wouldn't neglect the basic principles. We want to be expansive, but we cannot forget the basics."
De Villiers wouldn't elaborate about any possible changes, but Ricky Januarie has served his disciplinary time and is set to return at half-back, while Victor Matfield should get a run at lock in front of his home crowd.
Springbok captain John Smit, prop CJ van der Linde, loose forward Danie Rossouw and wing Tonderai Chavhanga will sit out Monday's scheduled training session as a precautionary measure.
Winger JP Pietersen and hooker Schalk Brits would remain with the squad, Pietersen working on his conditioning and Brits because of captain John Smit's commitments to Clermont, which means he will miss the Test against Italy on June 21.