Because when you get out played by a mile in 2 matches but happen to snatch a win, whilst the opposition wastes a hatful of chances, then you can hardly call it great victory.
The players will know in their own minds just how far away from barcas capability they really are.
Dont get me wrong, the end result was a great one for chelsea. But its not as though they went to barca, set their stall out and played the chelsea way, unless the chelsea way is a flat back 10.
They did this at home too.
Usually you go out to win a game by being better than your opponents, the only sense that Chelsea were better is that they took 3 of their 4 chances, where barca missed a redicolous number of easy chances, hitting the bar, post on numerous occasions.
Chelsea got lucky, but did what they needed to do.
Im not saying their effort and workrate etc should not be commended, but it was not a pretty performance, and they proved nothing about their own style of play or the ability of their squad.