"We know here the pitch is big and we have to stay together and try as hard as we cannot to concede goals and to go for the counter-attack as well", Willian told the club's website (www.chelseafc.com).
With home advantage and momentum gained from a dominant La Liga campaign, which sees them head the Spanish league by eight points, Barcelona are overwhelming favourites to win the tie.
Despite not quite bossing possession in their usual fashion, Ernesto Valverde's side wrapped the game up in the 63rd minute, when Lionel Messi netted his second goal.
It was nearly a tactical masterclass from Antonio Conte in the first leg, but one lapse of concentration from Andreas Christensen undid all their hard work.
Conte insisted he would not be happy if Iniesta is ruled out.
Barcelona, meanwhile, hand a start to Ousmane Dembele, with the €105 million summer signing from Borussia Dortmund making just his second European appearance of an injury-hit campaign.
Messi returns to the squad having missed Barca's last game for the birth of his third child, while Andres Iniesta took part in training on Monday and could be involved.
Conte said Antonio Rudiger is in contention after recovering from muscle fatigue but Ross Barkley (hamstring) and David Luiz (ankle) are out.
Once in the area, Messi picked out Dembele, who seemed to put every ounce of frustration from his injury nightmare this season into a vicious, rising right-footed finish. At the end, I must be pleased for the commitment of my players.
Of course, why change a winning formula at this stage of the competition, especially in a game where you want to avoid conceding.
'I definitely look out for Chelsea's results because I still have friends here.
The Italian manager described their performance in the first leg as one that has given his team the confidence to beat Barcelona.
Unlike the first leg at Stamford Bridge where the Catalan side could only create only a chance at goal, this time round Messi and co should create more meaningful scoring chances.