Everton boss Roberto Martinez has warned his stars to think twice about quitting Goodison Park.
Martinez cited Michael Owen's move from Liverpool to Real Madrid as an example.
He said: "Every time you have a good player, you're going to expect to lose him because they think that the grass is always greener elsewhere.
"It's a different challenge, the family wants to move to a better climate. Of course, players will always like that next challenge and to go to play Champions League football and to win trophies.
"But there are other great stories about that. Michael Owen leaves Liverpool to go to Real Madrid to win trophies and Liverpool win the Champions League.
"In football, nothing is guaranteed. Clubs need to be strong, and be allowed to be stronger than the players."
