Stuttering Borussia Dortmund ended 2016 with an unbeaten home league record, but a 1-1 draw against Augsburg means they could be as many as 12 points adrift of the Bundesliga leaders heading into the mid-season break.
Thomas Tuchel's side's only loss at Signal Iduna Park in the calendar year came in the DFL-Supercup to Bayern Munich in August and, with Carlo Ancelotti's leaders facing second-placed RB Leipzig on Wednesday, Dortmund had the chance to crank up the pressure.
Mario Gotze fired an early warning by hitting the post, but the hosts' defence has been suspect at times this season and so it proved again when Ji Dong-won - who had a spell at Dortmund in 2014 - finished a swift Augsburg counter-attack to put the visitors in front.
Pierre-Emerick Aubameyang, the league's top scorer, perhaps should have levelled before half-time, yet Ousmane Dembele's calm finish did restore parity shortly after the restart.
Shinji Kagawa will feel he could have had a penalty and Aubameyang and Andre Schurrle missed chances as Tuchel, taking charge of his 50th league match with Dortmund, was left frustrated.
Dortmund - who last went unbeaten at home in the Bundesliga in a calendar year in 2002 - now have just one win in five league outings and are fourth, nine points adrift of Bayern and Leipzig, while Augsburg - whose interim coach Manuel Baum has four points from two games - are 12th.
An impeccable moment of silence was held before kick-off in honour of the victims of Monday's attack in Berlin.
Dortmund enjoyed the better of the opening exchanges and Gotze rode a couple of challenges on the left of the box before seeing a deflected shot hit the near post.
Aubameyang then tested visiting goalkeeper Marwin Hitz with a low, dipping 30-yard free-kick.
Augsburg gradually started to pose questions of their own, although Hitz had to palm away Kagawa's stinging edge-of-the-box drive.
But it was the visitors that took the lead in the 33rd minute. Martin Hinteregger led a swift counter and Daniel Baier picked out Ji, who smashed into the unguarded goal after Roman Weidenfeller saved his initial shot.
Aubameyang wasted a great chance to level when he headed Marcel Schmelzer's pin-point cross wide of the left-post when unmarked in the area.
Marc Bartra saw tentative penalty claims for a shove from Dominik Kohr waved away as Dortmund remained frustrated at the break.
It took little over a minute of the second half for Dortmund to level, though. Kagawa slipped in Dembele, who took a touch and coolly slotted into the bottom-left corner.
Dortmund poured forward in search of a second and Hitz made a fine stop from Aubameyang's wonderfully controlled acrobatic volley, before Kagawa was unfortunate not to be awarded a penalty from Paul Verhaegh's trip.
Aubameyang's miscued effort caused panic in the Augsburg goal and the pacy forward was uncharacteristically wasteful with a high-and-wide effort when one-on-one.
Hitz foiled Aubameyang again in the closing stages with Schurrle placing the rebound wide as Augsburg held on for a point.