Both featured in their FA Cup win over QPR.
The manager said: "We have been very open from the beginning. Today you saw two players in Nikica and Johnny who have incredible experience and have been instrumental in our day-to-day working at the training ground.
"They are extremely pristine professionals and I need to listen to them. They are frustrated with the lack of minutes with the World Cup around the corner and I need to look into that. That doesn't mean we want to sell them.
"As a football club, if there are any offers or opportunities for the players, we will look into it, but it has to be right for the squad and the Club for anything to happen. We want to finish the window stronger than we started.
"We have been open from the start. They are vital members of this squad and that will be the case until it changes."
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