Borussia Dortmund coach Jurgen Klopp has admitted last season's Champions League's finalists have fallen on hard times after slumping to their third consecutive home defeat in the Bundesliga.

Hertha Berlin's 2-1 win at Dortmund on Saturday was the third straight home league defeat Borussia have suffered at the Westfalentstadion -- the first time that has happened in 13 years.

Dortmund dropped to fourth -- outside the automatic Champions League places -- as Borussia Moenchengladbach drew 2-2 at home to VfL Wolfsburg on Sunday to go eight games unbeaten.

"One must always be grateful and humble in life, these great lads have already written some great stories this year -- today it was different," admitted Klopp as the Bundesliga breaks for winter.

"This is a shitty end to 2013."

With the Bundesliga now on a winter break, Dortmund finish the year 12 points behind league leaders Bayern Munich, who have a game in hand.

Borussia's current form is a far cry from last season's eye-catching football which carried them through to May's Champions League final where they lost 2-1 to Bayern.

Dortmund have suffered five defeats in the first half of the season -- the most in the same period since Klopp took charge five years ago.

Having lost at home to Bayern, Bayer Leverkusen and Hertha, Dortmund are already effectively out of the title race.

A catalogue of injuries has blighted Klopp of late, especially to his first-choice centre-back pairing of Mats Hummels and Neven Subotic, who is out until May with a torn knee ligament.

It has meant 18-year-old Marian Sarr, who made his Dortmund debut in the 2-1 Champions League win at Marseille, has broken into the first team, but it was his mistake which led to Berlin's second goal.

After Germany winger Marco Reus gave Dortmund the lead, Colombia striker Adrian Ramos pulled one back, after a mistake from Dortmund left-back Erik Durm, before Hertha took the lead with 45 minutes gone.

When Sarr slipped in possession, Tunisia striker Sami Allagui pounced on the error and sprinted around Dortmund goalkeeper Roman Weidenfeller to roll the ball into an empty net to Sarr's dismay.

Klopp admitted he was looking forward to the winter break, which should see the return of Hummels and midfielder Ilkay Gundogan, as Borussia prepare for their training camp which starts January 5.

"Then we can start from scratch," said Klopp, whose side had 18 shots on goal to Berlin's six.

"We had our chances, we just didn't recognise them or use them.

"Today was only our smallest problem, the whole year has been very intense for us, particularly the last third.

"We have set high standards and all the matches we lost this season we didn't need to lose."

The focus now for Klopp is on facing Zenit St Petersburg in the last 16 of the Champions League and the quarter-final of the German Cup -- as well as recapturing last season's form.