Ronald Koeman has warned Gary Neville, declaring the Valencia coaching job as "extremely complicated" following his appointment on Wednesday.
Southampton manager Koeman lasted just six months at the Mestalla despite lifting the Copa del Rey trophy with a 3-1 triumph over Getafe.
"It's a very difficult place to manage," Koeman said.
"When I was there it was extremely complicated, nothing worked. And it is still complicated now.
"It is important to learn the language. Does he speak it? I don't know. He has his brother [Phil] there but it is not the same if someone has to translate for you. Even so, working with his brother will be special."
Neville will take charge of the La Liga outfit following their home fixture with league leaders Barcelona on Saturday.
