Both defenders arrived last summer from abroad.
"There is competition with Erik," Muniesa told The Sentinel, "but also with the centre-backs because I can play at centre-back as well.
"We have very good players making a great team and a great group of people.
"So it is always difficult to fight with friends, but it is what you have to do in football and also it is better for the team if it helps us play well."
But he can't deny a special affinity with Pieters after quickly developing a close bond with the affable Dutchman.
"It (England) is good for me. It was difficult at the start, but my girlfriend came, there was Erik, and also my family and friends came to see me.
"With Erik, we came together (to Stoke) last year, but with every player you are so close, centre-backs and right-backs as well.
"But we also know we have to fight for the position in defence. It is football."
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