The Red Devils' triumph ensured they fully capitalised on City's 3-3 stalemate with Sunderland at the weekend, meaning the current champions are five points clear at the summit.
Ferguson was delighted with the character demonstrated by his charges, in particular highlighting the importance of Valencia's breakthrough and labelling the winger "the difference between the sides".
"It was a long night, we had to persevere and persevere and we got our reward in the end but I have to admit that I thought for a long time it wouldn't come because we didn't make many clear-cut chances," Ferguson said.
"That goal [from Valencia] is so important and it perhaps typifies the history of this club that we kept going and got our reward in the end.
"Scoring so late, it's typical of us, our history. We never stop trying, there's no question about that. It could be a very important moment.
"It was a big performance from us because Blackburn possess a great threat. They can hit the ball long and catch you on the break and they have a real goal threat about them, so to come through what was a very difficult game is an achievement.
"When Ryan Giggs came on [as a second-half substitute] he made a difference and when Ashley Young came on he made a big difference and we got there in the end.
"The important thing now is to win Sunday's game [against QPR]. But listen, they are all big games now. It doesn't matter if it is next Sunday, the following Wednesday [at Wigan], the Sunday after that [against Villa], they are all big ones.
"The players are prepared for that. We will fight right to the end in all the games for the right to win."