Ireland were dealt a harsh 201 run defeat against South Africa.
Hashim Amla was in fine flow against Ireland and scored a mammoth 159.
According to de Villiers, South Africa performed well because they played Ireland to their merit.
It was Ireland's first defeat in three matches following wins over West Indies and the United Arab Emirates.
South Africa posted their 2nd consecutive 400-plus total as they beat Ireland by 201 runs.
"We did it against the West Indies, UAE and here again today, and against Zimbabwe it's not going to be any different," said William Porterfield.
The South African skipper showered praises on the batsman after the latter's 159-run knock.
Hashim Amla scored 159 off 128 balls to become the fastest man to reach 20 ODI centuries.
It was an all-round performance by South Africa as the outplayed Ireland in every deportment.
While chasing 412 to win, Ireland were struggling at 157 for seven at the end of 33 overs.