Gareth Bale did a lot of the damage to the Rover’s defence, he netted twice and also set up Roman Pavlyuchenko with his effort, eter Crouch also got in on the act, he scored his first of the season in the Premier League.
Blackburn did pull a couple back, Ryan Nelsen was the last one to touch David Dunn’s shot and in injury time, Gael Givet added a second.
Allardyce said: "The game from my point of view as a defensive unit was diabolical and as an attacking unit very exciting.
"But it is no good gifting the opposition four goals before you start putting the ball in the back of the net. We are very disappointed about the way we defended.
"We gave ourselves too bigger mountain to climb by not doing the basic defending right, which is unlike us, unusual, but unfortunate, and we will just have to take it on the chin."