A late Victor Boniface leveller has maintained Bayer Leverkusen's unbeaten record in the Bundesliga with a 1-1 draw at home to Borussia Dortmund.
With second-placed Bayern Munich's home game against bottom side Union Berlin postponed on Saturday due to snow, Xabi Alonso's Leverkusen had an unexpected chance to extend their lead at the top.
But they were stunned in the sleet after just five minutes when Norway full-back Julian Ryerson netted after a fine team move by fifth-placed Dortmund.
The hosts dominated but could not get past the mighty Mats Hummels in Dortmund's defence until the introduction of Patrik Schick on 79 minutes.
The giant Czech found space in the box - with Hummels for once outfoxed - and with his first touch squared for Nigeria striker Boniface to tap home his eighth Bundesliga goal of a productive season.
"We deserved to win the game so we are unhappy with the result," Alonso told broadcaster DAZN. "We've just got to stay cool now."
Florian Wirtz thought he had levelled for the hosts just before the break but a VAR review showed Boniface had been offside when flicking the ball on earlier in the move.
Leverkusen have now won 11 and drawn two of their 13 Bundesliga games, a club record, but the Dortmund draw leaves them only three points above champions Bayern - who now have a match in hand.
Second-bottom Mainz earlier lost for the first time under interim coach Jan Siewert as Michael Gregoritsch's goal sealed a 1-0 win for visitors Freiburg.
Siewert had picked up five points from his first three games since replacing the sacked Bo Svensson.
Despite the defeat leaving Mainz in the automatic relegation places, Siewert will stay as interim coach.
"He will be in charge until the mid-season break for sure. Then we will sit down together. He is in pole position," sporting director Christian Heidel told DAZN.
Freiburg narrowly missed out on a Champions League spot last term but have been less consistent this season and move up to eighth after a first win in five league games.
In the late game, ever-improving Augsburg beat a fitful Eintracht Frankfurt 2-1 at home to move into the top half.
Australian Associated Press