While the German said that he is not yet thinking about a move away, he did suggest that his long-term future is far from certain.
"I'm not considering myself with other clubs because the situation doesn't currently oblige me to," he told Sport1.de.
"Football is my job and all that matters is the present, the next game. I am not going to be wasting time considering what I do next. Barca are a great club and things can still change between now and the summer.
"If the situation remains the way it is at the moment, however, then we're definitely going to have to talk - there's no avoiding that."
Liverpool have been linked with the former Borussia Monchengladbach man.