The coach confirmed his admiration for the midfielder, who is surplus to requirements at Spurs, but is unsure of whether or not they can afford the 23-year-old
The Bundesliga side are weighing up a transfer for the 23-year-old, with both a loan or a permanent deal possibilities.
The midfielder is surplus to requirements at White Hart Lane after being loaned out to Fulham for the second half of last season, with former Spurs star Rafael van der Vaart keen for him to come to the Imtech Arena.
However, while revealing his admiration for the player, Slomka cooled hopes that the club could pull off the transfer.
"Holtby is a class player," he told Bild. "That is not up for discussion.
"But I do not know if it is economically feasible."