Borussia Dortmund coach Jurgen Klopp has refused to declare the Bundesliga title race over even though closest challengers Bayern Munich have all but given it up. Dortmund beat Bayern 1-0 last night with a 77th-minute goal from Robert Lewandowski to extend their lead at the top to six points with four games remaining. But with a trip to local rivals Schalke to come on Saturday, Klopp is not getting carried away. "Unfortunately, a lot can still happen," he said. "We now have three days to celebrate this extraordinary feat and to enjoy it. "Then we have the next obstacle in front of us. Our friends in Gelsenkirchen will do all they can to make things hard for us. When things are decided, then you will see us celebrating, but until then, we will just be working hard." Bayern will reflect on a poor individual display from Arjen Robben as one of the reasons why the title race took a potentially decisive turn in the wrong direction. The Dutch international winger had the chance to cancel out Lewandowski's goal from the penalty spot with four minutes to go after being brought down by home goalkeeper Roman Weidenfeller but his weak effort was easily saved. He was then presented with an open goal at the death but shot over the bar. "It is very disappointing," Robben said. "I don't know what I should say. I have scored ten or 11 penalties in a row over the last three years and today's was the first I have missed. For that to happen in such a moment is bitter - yes, it is embarrassing. Dortmund have taken a huge step and we can almost say that they are champions." Bayern chairman Karl-Heinz Rummenigge felt Robben was the wrong man to take the spot-kick. "For me, from a coach's perspective, he shouldn't have taken it," Beckenbauer told Sky television. "I believe in the rule that the player who is fouled should not take the penalty. Maybe that's not the rule anymore or it's not yet reached the Netherlands. We have strong enough penalty takers like (Toni) Kroos and (Bastian) Schweinsteiger." He added: "Dortmund will, like last year, be deserving champions."