Schalke were held at home by Mainz as a former Borussia Dortmund striker did his old club a favour.
Mohamed Zidan moved from Schalke's local rivals to Mainz on transfer deadline day and he put the visitors in front in the 15th minute, making a dream debut for Thomas Tuchel's side.
But Chinedu Obasi's first goal for the Royal Blues earned them a share of the spoils, taking them up to second ahead of Bayern Munich, but leaving them two points behind Dortmund at the top of the Bundesliga table.
Schalke had both Raul and Benedikt Howedes back in their team after both returned from injury while Zidan was in the Mainz team for his third debut at the club following his return from Borussia Dortmund.
The Egyptian made a dream start to what he says will be a long stay with Mainz this time, putting them ahead in the 15th minute.
Radoslav Zabavnik sent in a swinging cross from the left and Zidan met it confidently on the volley to beat Lars Unnerstall in the Schalke goal.
Only moments earlier, Zidan went within inches of scoring with a free-kick from over 30 yards out.
Mainz did not stop attacking there either and Schalke appeared shocked in their own back yard.
It took them over half an hour to get going, but then they started to attack more insistently with Mainz showing their defensive strength to match their attacking incision.
Jefferson Farfan and Jose Manuel Jurado were both introduced by Schalke coach Huub Stevens at the start of the second half and it was clear Mainz were in for a tough 45 minutes.
Their resistance was broken after only 14 minutes when Obasi showed just why Schalke had signed him from Hoffenheim as he dribbled his way towards goal and then curled the ball inside Christian Wetklo's near post with the outside of his left boot.
Joel Matip headed wide as Schalke laid siege to the Mainz goal in search of a winner.
But despite attack after attack, they were unable to find a winner at the Arena AufSchalke where their title hopes suffered a setback with just a draw, ending a run of five straight wins.
