Klopp blamed wastefulness in front of goal for the Bundesliga defeat, stating that Die Borussen had enough chances to claim a point but said that "was not to be".
"Congratulations to Schalke for a deserved victory, but for us it still feels unnecessary because we had some very good moments in our game after Schalke had taken the lead," Goal.com quotes Klopp as saying.
"Whenever we were determined, we were dangerous, but we did not take our chances.
"A draw would not have been undeserved, but it was not to be. Schalke used their good half to get two goals, but our good phase could only muster one. Therefore, we deserved to lose."
Robert Lewandowski scored Dortmund's only goal.