Zlatan Ibrahimovic's double - split up by goals at the very start and end of the game from Blaise Matuidi and Yohan Cabaye respectively - saw les Parisiens put one foot firmly in the Champions League quarterfinals with the first-leg win.
The Bundesliga side need a miracle at Parc des Princes in the second leg, though the Finnish coach denied that his players were entirely to blame for the four-goal thrashing.
"You can't say that it all went wrong. You also have to look at what kind of team we faced," Hyypia told reporters. "PSG are a top-class opponent and they were excellent. If you fall behind after three minutes it is always difficult to fight back."
Emir Spahic was sent off for Leverkusen on the hour mark and Hyypia said his team reacted well to the red card, even suggesting it was better off being a man down.
"It became very difficult and we never found our usual rhythm during the first half," the Bundesliga coach added. "After their first goal it took us 15 to 20 minutes to get back into the game. In the second half we had a man sent off and I felt that we were better with 10 men than 11."