Do you really want to watch a Barca game where we are looking for a nil all draw. This is Barca not Chelsea or juventus. Too risky if they scored a late one. Always go looking for goals and Roberto should play in midfield and semedo right back if iniesta doesn't make it
Yes, we should have an attacking mindset, and I will be surprised if we don't have that - also in the starting-11. But it is tricky with both Semedo and Iniesta out.
I'm sure Iniesta would contribute in attack if he could start, and that Semedo+Roberto+Dembele would play if Semedo was ready. Valverde needs to come up with other attacking solutions, although a think a straight 4-3-3 with Raktic and Gomes would be too weak, but maybe we have no other choice?
Chelsea are vulnerable right now, especially in defence with Christensen a bit shaken right now - they are playing bad and with no motivation (the latter will change against us).
So we should go after the kill - a lot of Chelsea-players will be frustrated as
1) They don't play CL every year, so there is no coolness and decisiveness about them
2) Who knows if they will play CL next year because of there bad PL-spell right now
3) This is the biggest Chelsea can hope for this seasono (FA-cup wouldn't save them).
All that taken into account: We should play an attacking team and go for the early goal to settle this, because then Chelsea would play right into our hands with desperate attacks or a frustration-red-card or the likes.