Huth has been a regular in the Potters' back four since joining them from Middlesbrough in 2009, but he now faces increased competition for a starting spot next season under new boss Mark Hughes.
Muniesa can play at left-back or in the centre of the defence, while Pieters is primarily a left-back.
Huth told the club's official website: "It's always good to have someone to hopefully improve your game.
"Game on - everyone's place is up for grabs. All the positions that were occupied last season are there to be taken with a new manager. I've got to keep my head together and stay fit and see what happens.
"I've seen both Erik and Marc play on TV and I'm looking forward to meeting them on Monday when we report back."
Huth is raring to go as he prepares to return to training after doing some additional fitness work over the summer.
The 28-year-old Germany international added: "I like to do a bit of hard work before we report back, so next week when we do start officially I won't get the aches and pains that I normally get.
"I personally look forward to pre-season. It's a chance to get away with the lads, we are going to the United States for almost two weeks and to France as well I think. It will be hard work, but it's something to enjoy as well."