Mancini saw Marco Materazzi sent-off before halftime as the Reds stormed his defence in the final minutes through stunning goals from Dirk Kuyt and Steven Gerrard.
"I was already a little frightened after the first two yellow cards for Cristian Chivu and Materazzi, as having both central defenders booked within 10 minutes is dangerous," said Mancini.
"Liverpool hadn't created much, but kept us under pressure, so with 10 men for an hour my team could not have done more. Unfortunately the last five minutes proved decisive."
"Inter came on the field determined, but Liverpool put the pressure on in the opening 20 minutes, which is understandable on their home turf.
"Patrick Vieira unfortunately is not match fit, so I needed him more in the second half, hoping of course that we were XI vs. XI."
Yet Mancini has some hope, as the only other time these teams crossed paths was in the 1965 European Cup.
Inter lost 3-1 at Anfield and won the second leg 3-0 at San Siro, going on to lift the trophy.
"It seems a coincidence, but perhaps the past comes back. We need three goals to qualify and clearly this side is capable of it, but we need to finish the match with all our players.
"I think the biggest problem we had here was being left with 10 men, but even then we didn't run many risks and only conceded the first goal with a deflection off Maicon.
"When we lined up with four in midfield we were under more pressure, as Zlatan Ibrahimovic on his own upfront had a tough job. Cordoba's injury was also damaging, as he was able to contrast Peter Crouch in the air."