Bayer were put on the brink of Champions League elimination by a rampant PSG side thanks to two goals from Zlatan Ibahimovic and one strike apiece from Blaise Matuidi and Yohan Cabaye.
To make matters worse for Hyypia, it was his side's third home defeat in the space of a week following losses to second-tier side Kaiserslautern and Schalke in the DFB-Pokal and Bundesliga respectively.
Hyypia said on kicker.de: "We have defended the entire season this way and have not conceded many goals.
"We have conceded the second fewest goals behind Bayern.
"Maybe we will have to come up with something else."
Hyypia was frustrated that his gameplan never had the chance to work after Matuidi's goal put them behind in just the third minute.
"We found it tough after going behind so early against a top team," he told the club's official website. "We wanted to be compact at the back and switch play quickly but I didn't see much sign of that in the first half."
Out of the cup and with their Champions League hopes now realistically over, Bayer must steady the ship and find form quickly if they are to maintain second place in the Bundesliga.
Things do not get any easier however as they face a trip to Wolfsburg this weekend.
Sporting director Rudi Voller said: "The 4-0 loss obviously hurts after the defeats against Kaiserslautern and Schalke. We need to get back on track against Wolfsburg."