Left-back Pieters joined Stoke from PSV Eindhoven in June, and was quickly followed through the door by Barcelona defender Marc Muniesa.
|11/4||Stoke are 11/4 with BetVictor to be relegated next season
"Looking at the squad it was evident to me there was a lack of naturally left-footed players," Hughes told reporters.
"We needed to address that, and there were good opportunities to bring in the right quality as well.
"Erik is a bit older and a little more experienced than Marc, but both have played at a good level.
"Erik has played at a top club in the Dutch league so technically, as you would expect, he is very good. He is a player I think will adjust very quickly to the Premier League.
"Marc is a young man who has made a big step. He has come from one of the top clubs in the world to try to make his career in the Premier League.
"It is a big decision, but I have been impressed with him. I think we have a very good player on our hands.
"His technical ability is without question, he just needs now to adjust to the Premier League."