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The key to Chelsea's progression to the final could well be decided by how well they defend set pieces.
As slick and exciting as Basel often looked on the attack against Spurs, the Swiss side have actually struggled be penetrate opponents in open play, scoring just five of their 16 goals that way.
Instead, they benefit from disjointed games and thrive on set pieces, where they have already scored seven goals and another three penalties—more than any other side in the tournament.
Chelsea are strong at attacking set pieces but are not always as cohesive in the air at the back. Rafa Benitez's side will need to be organised and prevent as many dead-ball opportunities as possible to stifle their opponent's primary strength.
If they can do that, Basel will find it hard to score, especially at Stamford Bride.