The BayArena chief was embarrassed with how his side crumbled against PSG on Tuesday and believes conceding in the opening minutes proved to be their undoing
PSG midfielder Blaise Matuidi opened the scoring early on before star striker Zlatan Ibrahimovic netted twice, with January signing Yohan Cabaye adding a fourth goal with two minutes left on the clock.
The defeat leaves the Bundesliga side all but out of the Champions League ahead of the second leg of the last-16 tie and Voller said he was embarrassed by the performance.
"It's always hard to comment after such a match," he told Sky after the game. "Such a loss hurts.
"To lose against a top-team like PSG isn't that much of a big deal. But it looks stupid now with us losing 4-0.
"We must turn things around now. If you go behind after two minutes it's lethal."
Sami Hyypia's men face PSG at the Parc des Princes in the return leg on Wednesday March 12.