A goal from Nigeria striker Victor Boniface with 11 minutes remaining ensured Bayer Leverkusen a 1-1 home draw with Borussia Dortmund on Sunday, keeping the league leaders' unbeaten record this season intact.

Dortmund scored just five minutes in through Julian Ryerson and the visitors looked set to be the first side this season to beat Leverkusen in any competition.

With the clock running down, Leverkusen manager Xabi Alonso brought Patrik Schick from the bench and the move paid immediate dividends, with the Czech attacker finding Boniface for the equaliser.

The draw means Leverkusen end the round three points ahead of Bayern Munich on the ladder, although the Bavarians have a game in hand after Saturday's match with Union Berlin was postponed due to heavy snowfall.

Alonso made eight changes to the XI which won 2-0 at Swedish side Hacken on Thursday, which secured them top spot in their Europa League group.

Coming into the match 10 points behind Leverkusen after just 12 matches, Dortmund were hit with a pre-match wave of the flu, ruling out several first teamers including Donyell Malen, Niklas Suele and Ramy Bensebaini.

Fresh from Tuesday's 3-1 win at AC Milan which secured progress to the Champions League knockouts, Dortmund burst out of the blocks, taking the lead after just five minutes through Ryerson.

With his back to goal, Niclas Fuellkrug held the ball up perfectly before back-heeling to Ryerson, who threaded the ball into the goal.

Leverkusen turned up the heat for the remainder of the opening half but could not find an equaliser, Florian Wirtz's 45th-minute stunner being ruled out by VAR for a narrow offside.

Dortmund held firm amid relentless Leverkusen pressure in the second-half, before Alonso sent on Schick, who had only played one minute in the league this season.

The Czech striker helped Leverkusen equalise less than a minute later, sliding a ball through the Dortmund defence to Boniface, who tapped home from close range.

Earlier on Sunday, a second-half goal from Austria striker Michael Gregoritsch took Freiburg to a narrow 1-0 win at struggling Mainz.

Despite the scoreline the match was ripe with chances, Mainz going closest in the first half through Sepp van den Berg, while Gregoritsch was denied twice by the post.

The 1.93-metre-tall Austrian scored with 20 minutes remaining, hammering in on the turn to give his side the lead, his first league goal since May.

Mainz's Leandro Barreiro was inches away from an equaliser with just a minute remaining, but the visitors cleared the danger.

The win, Freiburg's first in the league since October, sends the Europa League participants into eighth place while Mainz remain mired in the relegation zone.