He said: "In 2000 I was in a similar situation at Leverkusen, but we were the ones leading and Bayern Munich caught us," said Ballack. "In the last game we were three points in front, but lost the game and the title.
"It can happen up to the last minute. The pressure is on them because last week they looked like they were the champions. They had a five-point lead and now we have closed the gap.
"It was our best performance, especially in the first half. We passed the ball and didn't just use long balls. We moved the ball very well in this game and showed we can play good football.
"Manchester United still have everything in their hands but the pressure is on them. It looked like they were champions, but now it's getting smaller and tighter. Nobody expected Chelsea to be in this position now or in the Champions League."