The 20-year-old midfielder continues to be heavily linked with a summer exit at Selhurst Park, with Swansea City said to be leading the chase for his services.
The Wales international has hinted that he would be open to such a switch, and his national team coach Chris Coleman says it would be ‘a great move’ and ‘would make a lot of sense’.
Williams is eager to find regular first team football having been starved of action at Palace last season and ending the campaign out on loan at Ipswich Town.
Pulis has, however, informed the youngster that he still has a part to play at the Premier League outfit if he proves that he is willing to scrap for his place and ignore the transfer rumours.
He told the South London Press: “Jonny is a Crystal Palace player until deemed otherwise.
“He’s one player that there is always going to be speculation about that he could be going – you are never going to take that out of the game.
“If people want to talk about it, then they will talk about it. But Jonny comes back at the same time as the rest of the players.
“It is his responsibility to come back and do as well as he possibly can to get back in the team.
“He is a great lad and has got the potential – that is the word to use. He has got to fulfil that potential.”
While attempting to quash talk of an impending exit, Pulis has also pointed out that he is working hard to bring fresh faces into the Palace ranks.
He added: “There is lots of stuff going on behind the scenes.
“I’ve always tried to get things lined up and then you hope that things drop in place for you.
“There is work going on that people never see – it is busy.”