Villas-Boas seemed determined to undertake a mass clearout at Stamford Bridge.
Asked if he had tried to change too much too soon, Lampard said: "It's hard to pinpoint things. I don't want to go too much over negatives.
"We didn't perform to a level, that's why the manager changed and us, as players, are not happy because you don't feel as proud as you should be when you know the squad we've got should be doing better.
"So the reasons are not quite clear but there's a lot to be said for having a confident squad.
"You have to have that to get the best out of all your players and I feel we are in a better position now than we were in the past."