The Blues finally delivered a performance to give Barca cause for concern on Sunday night, three days before the teams meet in a mouthwatering Champions League semi-final first leg at Stamford Bridge.
Chelsea's chances against the all-conquering Spanish and European champions were written off the moment the draw was made but Lampard said: "From the start of every game, it's 50-50.
"Barcelona are favourites because of the players they have in their team but if we play like we did against Spurs in the two games then we will have a chance.
"It gives us confidence. We have to carry that on.
"There's no point in resting on that because the game on Wednesday's huge.
"We need to take that into the Champions League games and all the rest of our league games.
"Any team's beatable. They are the best, but we can't show too much fear.
"We have to take them on and I think we can do it."