Busquets went into the book after 49 minutes for a foul on Dries Mertens that means he picks up a one-match ban and will miss the return leg at Camp Nou.
Arturo Vidal was sent off late on after picking up two yellow cards in quick succession. The Chilean was booked for a late foul on Mario Rui and then leant his head into the left-back.
Nelson Semedo was the only other player at risk of suspension but came through the match unscathed and will be available.
Barcelona head into the match with the advantage after a 1-1 draw at the Stadio San Paolo in the first leg but are short of numbers due to injury and suspension.
Mertens gave Napoli the lead with a curling strike in the first half. but Antoine Griezmann’s away goal means the Catalan giants will be favourites to progress given their home form.