Kai Havertz has been told to ward off the advances of Bayern Munich and continue his development at Bayer Leverkusen by former Germany captain Michael Ballack.
The 20-year-old midfielder has been strongly linked with a move to the Bundesliga champions, as well as Liverpool, Manchester United and Manchester City.
But Ballack, who played for both German clubs as well as Chelsea, believes Havertz has aspects of his game which need to develop at Leverkusen.
'He is an exceptional player, but one thing is also clear.