Liverpool boss Jurgen Klopp refused to rule out the possibility of letting midfielder Jordan Henderson leave Anfield this summer.
The England international has been linked with a surprise move to Tottenham recently, and Klopp was asked about the speculation in his press conference ahead of the Reds' game against Southampton this afternoon.
"Everything is OK in this moment but nobody in the world, maybe only [Lionel] Messi, is unsellable," Klopp told reporters. "There is always a situation. I come from a club where always the best players are picked by other teams and at the end, you have to accept a few things and always need to have a Plan B or C.
Henderson joined Liverpool from Sunderland in a £20 million move back in 2011.
Klopp continued: "I am pretty sure it is only a rumour [Tottenham wanting Henderson] but if not and if a player -- let's not say Hendo but any player -- comes to me and says he doesn't feel comfortable and wants to leave, style of play, more money, then you always have to start thinking. That's all I can say on this.
"Coutinho, [Roberto] Firmino, so many players are very special. You could go through the whole squad. But if a player wants to go to another club then I'd always be open to it because I don't want to have a player in my squad who doesn't want to be in the squad.
"These are problems you don't need during a season. A player is never good enough for you to have to cope with problems like that for an entire year."
Liverpool currently sit in eighth in the Premier League, and secured their passage into the quarter-finals of the Europa League with a 3-1 aggregate victory over rivals Manchester United in mid-week.
Despite the fact that Klopp's side, who drew his former team Borrussia Dortmund in the Europa League, are seven points adrift of the top four, defender Dejan Lovren believes Champions League qualification via the league is still attainable this season.
"We have games in hand on other teams so it's important to win to be above Southampton and close to the other teams above us," he said. "We need to keep pushing hard and I definitely think and believe in our team that we can finish fourth."