Chelsea go into the second leg of their last-16 tie against the Liga leaders having drawn the first leg 1-1 at Stamford Bridge.
When asked about Chelsea's game-plan, Willian said: “We come here to do exactly the same job that we did at Stamford Bridge.
"We know Barcelona always have more possession. They like to have the ball and they like to play. But, like I said, with the ball we have to be more clinical.
"Without the ball, we have to stay compact like we did at Stamford Bridge. We all have to do the same job.
"We know here the pitch is big, and we have to stay together to make sure we don't concede goals, but to go for the counter-attacks as well."