Goal exclusively revealed that Spurs' £10 million demands have proved a stumbling block for the Bundesliga side, though they had hopes of taking the player on loan for the remainder of the season.
|7/2||Tottenham are 7/2 with bet365 to finish in the top four|
"We can't really imagine such a transfer financially. Talks have not yet reached an advanced stage," Keller told Bild.
"Lewis has already played as a defensive midfielder under me. He can play there and is tactically very well-schooled."
Schalke sporting director Horst Heldt meanwhile says that any talks have now stalled as Spurs are not interested in a loan deal.
"We have good contact to Lewis. He enjoyed playing with Schalke and he is not quite happy in London right now," he added.
"Tottenham do not want to let him leave on loan, that is why the deal is difficult. It makes no sense for us, spending a lot of money for a player who we sold a year ago because his contract was expiring.
"We are currently not negotiating with Tottenham."
Holtby has started just six Premier League games this season and just once under new manager Tim Sherwood.