The Argentina international scored his eighth and ninth goals in the group stage to seal his side's progress to the next round of the competition.
The Serie A leaders took another step towards retaining their title with a comfortable victory in Turin that leaves them with a healthy lead with just four games left to play.
The striker converted Augusto Fernandez's cross with a perfect header in the first half, and it proved to be the only goal of the game despite Athletic's efforts.
The Uruguay international scored four and laid on three more in a superb display at Estadio Riazor, setting a La Liga record in the process, with the Catalans in sparkling form.
The Swede has now scored 32 Ligue 1 goals this season, while Blaise Matuidi, Edinson Cavani, Angel Di Maria and Maxwell were all on target, too.
Xabi Alonso's corner was met by the Germany international's head to hand Die Roten the lead and his penalty later confirmed victory, as they ended the visitors' cup aspirations.
The Old Lady extended their lead at the top of Serie A with a comfortable win over Palermo, who remain in serious danger of slipping out of Italy's top flight.
A Robert Lewandowski brace and Arturo Vidal's goal helped Bayern Munich close to within touching distance of a fourth successive Bundesliga crown as they defeated Schalke3-0 at the Allianz Arena on Saturday.