Draxler's contract at Schalke does not expire until June 2018, but the attacking midfielder has been linked with a transfer, with Premier League leaders Arsenal said to be interested.
Keller's side sit seventh in the Bundesliga - four points adrift of the UEFA Champions League places - ahead of the resumption of the German season.
And the ex-Stuttgart boss feels the 20-year-old attacking midfielder should not rush into a transfer to a foreign league, and hinted that Schalke would be looking to receive a considerable transfer fee in order to part with his services.
"Julian has all the time in the world to go abroad," Keller told Bild.
"In order to exist there, one must be strengthened in his personality."
"And Schalke does not deserve peanuts."
Schalke travel to Hamburg for their first game since the mid-season break on Sunday.
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