I think you'll find that almost the whole team was having a mistake last night and singleling out one incident when the whole defence was a shambles is a bit harsh. Yes Dawson was caught but even your saviour Gallas would not of been able to turn and catch their forward from that position, and to be fair if Palacious hadn't given the ball away then nobody would of been caught anywhere. Bassong and BAE were caught for the 3rd goal in almost the same way so ce la vie !!!
yes I agree that the whole defence and central-midfield played badly.... but it wasnt helped (and greatly caused) by an inability to play well with the back4 pushed upfield - for the fear of being skinned on our rightside..
particularly for the 3rd goal, this caused our back4 to defend too deeply, leaving a chasm between our midfield and Back4 lines with huge holes for their players to flit into without being picked up...... the guy that scored the 3rd goal positioned himself 8-10yds in front of the Backline and still at least 5yds away from our midfield line, to pick up ythe ball..... that gap is simply too huge.... Bassong couldnt leave his post and go charging up almost into midfield and Modric (the nearest CM) couldnt in time go back to cover such a huge area where Constanza was....
very slow rightside ----> defending deep -------> big gap Back4 to midfield line (esp. when our midfield has to go forward to help get equaliser) ----------> very vulnerable in the space between Back4 and midfield (as shown in 3rd goal)..
the alternative when we are behind is to push that Back4 forward to close huge gap to midfield line, and be very vulnerable to pace on our slow rightside.... just ping the ball into the 40yd space behind Corluka and Dawson at will to get all the chances you need to score more goals....