"There are many upsets in cup competitions, which we have seen in the FA Cup," the former Borussia Monchengladbach midfielder told the matchday programme.
"You have to give your all against all sides, regardless of if they are in the second division, or the fourth, or the fifth. In football, things can happen quickly. Against the smaller teams, if they get a goal, it can be difficult to get one back. The cup is always good for a surprise, but we have dealt with that well so far.
"I remember when I was in my first year at Gladbach. We played against Darmstadt, who were in the fourth division at the time. We lost the game in a penalty shoot-out. We had to learn a lot from it. We went there, thought we would have some fun against a fourth-division team.
"We took the lead but then they equalised and nothing was possible anymore. But they fought for each other, they ran so hard for each other and we were all surprised. Penalty shoot-outs then come down to luck too - we lost and were standing there with big heads thinking 'what did we do wrong?'"