The 29-year-old has been the primary choice at the position since arriving from PSV Eindhoven in 2013. But recent loan acquisition Kostas Stafylidis has started the last two games, and Pieters has aired his concerns with Potters boss Paul Lambert.
He said: "I had a conversation with the gaffer and he said to me he wanted to see Kostas play. Of course I'm not happy but the main thing now is not about me, it's about the club and making sure we stay in the Premier League.
"You have to put yourselves second and the team first. If it means that Jack Butland has to play as striker, he'll just have to grin and get on with it.
"I'm not happy if I don't play. I want to play and do my part but hopefully I showed at Southampton that I will always be ready when I'm called on and I will fight for the side."