The Belgium international welcomed comparisons to the world's best on the eve of the mammoth clash at Stamford Bridge.
And Sky Sports Spanish football expert Terry Gibson has spotted a weak spot in the Barcelona back line which the Chelsea star can target.
Below he looks at where the first leg will be won and lost...
Sergi is vulnerable
Sergi is Barcelona’s first-choice right-back but his most natural role is as a midfielder, so he can look shaky when put under pressure by a positive wide player.
Takashi Inui, a Japan international, gave Sergi a tough day when Barça played Eibar at the weekend, beating him nearly every time in one-on-one situations. Inui is a good player but if he can cause Sergi so many problems, then imagine the damage Eden Hazard may be able to do.
Chelsea should give Hazard the ball at every opportunity— but they must not forget that Sergi is a real force when attacking. But Hazard, or Pedro if he plays wide, cannot neglect their defensive duties, otherwise Chelsea will be punished.
If Chelsea fans are expecting Barcelona to be slack across the whole back four, though, they will be disappointed. They have conceded only 11 goals in La Liga all season, while Real Madrid have let in seven in their last three league games alone.
Barcelona are much sharper at defending set pieces these days, and there is a real determination among these players to keep clean sheets, even when they are 2-0 or 3-0 ahead with little time remaining.
For example, they will do everything they can to snuff out an opposition counter-attack, even if a goal at that time would make no difference to the outcome of the game.
I don’t see a better central defensive pairing in world football than Gerard Pique and Samuel Umtiti, and Chelsea will have their work cut out to get past them.
Ernesto Valverde, the coach, was allowed to go for a more conservative style after Barcelona were thrashed by Real in the Spanish Super Cup last summer. So while Barcelona might not play as much thrilling football as they used to, they are just as formidable because they are so solid.
Beware Rakitic’s runs in the closing stages
Ivan Rakitic is not as well known to English audiences as his Croatia team-mate Luka Modric, but he is an extremely clever, adaptable player.
Don’t be surprised to see Paulinho sit alongside Sergio Busquets in central midfield for the first 70 minutes, keeping things ticking over and making only occasional bursts forward.
Then, depending on the game situation, watch him start making regular runs into Chelsea territory.
Paulinho, the former Tottenham player, does a similarly important job. Playing on the right of a narrow four-man midfield, Paulinho knows when to hold, when to tuck in, when to help his full-back and when to attack.
Chelsea must not be deceived by his two poor seasons at Tottenham.
Suarez is red hot once again
Last autumn I thought Barcelona should sell Luis Suarez. During the first part of the season, he was very poor. Not only was he struggling for goals, but he was finding it difficult to control the ball, beat defenders or find team-mates with simple passes.
I thought he was over the hill, but I believe his two-week stint of fierce physical training in November changed everything because now he looks like the best centre-forward in the world again.
Suarez’s return to form has eased the pressure on Lionel Messi, who has been more of a creator than a taker of goals in recent weeks.
The old guard are still vital to Barcelona: Philippe Coutinho is an excellent player but he is still some way short of the standard Andres Iniesta sets in the biggest games.
Iniesta has long been one of my favourite players and, if he were 23 rather than 33, I can only imagine what he might be worth.
Valverde trusts him completely, so when Iniesta wants to come off, he does. That relationship has allowed Iniesta to flourish again this season.