Napoli sit third in Serie A but have slipped virtually out of contention for the league title and a series of mediocre performances, including last week's scoreless draw in the first leg in Wales, have placed question marks over Rafael Benitez's side.

Despite Napoli enjoying home advantage, Swansea came looking for a result and were unlucky not to come away with more from the San Paolo.

The Premier League outfit sniffed an early opener when Marvin Emnes showed his pace down the right, drew out Pepe Reina and beat the 'keeper only for Raul Albiol to clear off the line.

Higuain shot over minutes later following Goran Pandev's delivery, but the Argentine helped make amends in the 17th minute when his glancing header allowed Lorenzo Insigne to beat the offside trap and lob Michel Vorm in the visitors' goal.

At the other end Wilfried Bony sent a header wide as Swansea started to build momentum, and leveller finally came when Jonathan De Guzman ran on to Bony's through ball and fired past Reina, although the Spaniard got a hand to his shot.

Napoli rode their luck throughout but Higuain finally restored the Italians' lead on 78 minutes.

Belgian Dries Mertens sent an innocuous-looking ball into the Swansea area, where a deflection produced a loose ball and allowed Higuain to fire past Vorm from close range.

Five minutes later Reina did well to save Dwight Tiendalli's header from a corner while at the other end Higuain missed a golden chance for his brace when set up by Marek Hamsik.

Napoli's nerves were only really settled when Higuain and Hamsik combined to set up Inler for the Swiss to score Napoli's third in the third minute of added time.

While Napoli progress to a tie against Porto, the Italian Cup holders Lazio were sent crashing out of the competition, conceding a late goal in Bulgaria to lose 4-3 on aggregate to Ludogorets Razgrad.

Two more Italian sides could progress later though, with Juventus and Fiorentina holding first-leg leads against Trabzonspor and Esbjerg respectively.