The former Germany international believes that the Bavarians need to stay relaxed amidst the Santiago Bernabeu atmosphere and warned against Los Blancos' attacking strength
Jupp Heynckes' men secured a 2-1 lead in the first leg at the Allianz Arena, and Kahn has urged his former team not to lose their focus in Wednesday's return clash at the Santiago Bernabeu.
"You have to make sure that you're not getting carried away. It's important to remain calm and relaxed, especially in such a partisan atmosphere," Kahn was quoted as saying by TZ.
"Real generally score a lot of goals in home games. They're always capable of netting two or three times at the Bernabeu. Bayern, however, are a team that you can rely on at any time. It's impossible to tell how things will go.
Kahn then conceded that the Bavarians would have been better off had they held Madrid to a goalless stalemate in the first leg.
"A 2-1 win in the first leg is not a good result. A scoreless draw is perhaps even better. But the fact that you've won is a confidence boost."
Wednesday's game at the Bernabeu kicks off at 19:45BST.
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