Bayern Munich coach Jurgen Klinsmann insists his side must build on their impressive 5-0 rout of Sporting Lisbon on Wednesday.
Two goals by Franck Ribery and Luca Toni, plus a single effort from Germany striker Miroslav Klose, puts Bayern virtually into the quarter-finals.
Now only a disaster in the return leg on March 10 at Munich's Allianz Arena will stop Bayern reaching the last eight.
But Bayern have lost three of their last four Bundesliga games, suffering a shock 2-1 defeat by Cologne in Munich last Saturday, and Klinsmann insists his side cannot dwell for too long on the result at the Estadio Jose Alvalade.
"This was a nice game to watch after the second goal went in - that is when I knew we had cracked them," said Klinsmann.
"We stand with one leg in the quarter-finals, we must not allow this position to slip.
"We have to put this victory behind us and remove the emotion from the occasion."
The German giants know they must make their huge advantage count back in Munich, however.
"Without arrogance we can look forward to the quarter-finals," added Bayern chairman Karl-Heinz Rummenigge. "The atmosphere in the dressing room was subdued, we know the job is only half done."