BERLIN, Dec 18 (Reuters) - Champions League competitors Schalke 04 slumped out of the German Cup in the round of 16 on Tuesday, suffering a 2-1 defeat by visiting Mainz 05 to continue their disappointing domestic season.
With new coach Jens Keller, who replaced Huub Stevens on Sunday, making his Schalke debut, the hosts showed few signs of recovery after losing four and winning none of their last six league games.
Schalke, who topped their Champions League Group to book a spot in the next round of Europe's premier competition, allowed the visitors to take a 30th-minute lead when Marco Caligiuri drilled in from 16 metres.
After a string of missed chances, Dutch striker Klaas-Jan Huntelaar drew them level but their joy was short-lived as Nicolai Mueller controlled a Jan Kirchhoff cross to fire in the winner seven minutes from time.
Schalke's Christian Fuchs rattled the bar late in the game but could not prevent the 2011 Cup winners' exit and their sixth straight game in all competitions without a win.
Freiburg also advanced with a 1-0 victory over third-tier Karlsruhe SC.
Bundesliga leaders Bayern Munich are in action against Augsburg later on Tuesday and holders Borussia Dortmund face Hanover 96 on Wednesday.
(Reporting by Karolos Grohmann, editing by Ed Osmond)