Giaccherini helps fire Napoli into Cup quarters

Napoli coach Maurizio Sarri and makeshift striker Dries Mertens were notable absences at the San Paolo due to both serving one-match suspensions and watched from the comfort of the executive boxes.

By the end of a dominant first half for the Serie A title challengers, Sarri had his head in his hands in frustration after Antonio Piccolo's deflected 35th-minute strike levelled Piotr Zielinski's well-taken third-minute opener for the hosts.

Spezia had eliminated Serie A strugglers Palermo in the previous round, but any hopes of causing an upset were quickly extinguished.

Zielinski exposed the visitors barely three minutes in after collecting possession on the left, cutting in unchallenged and beating Leandro Chichizola in the Spezia net with a superb curling strike at the keeper's far post.

Napoli should have doubled their lead, but were wasteful every time.

Manolo Gabbiadini had stepped in to replace Mertens and tested Chichizola with a fierce long-range strike on 24 minutes.

Lorenzo Insigne then hit the post with the softest of touches from Giaccherini's cut-back, and from the corner Zielinski forced Chichizola into a desperate one-handed tip over the crossbar.

Gabbiadini turned on the style, controlling well to drop a backheel into the path of Insigne only for his curling strike to inch agonisingly wide.

A Giulio Maggiore snapshot on a rare Spezia foray fired a warning to Napoli keeper Rafael, who after punching a dangerous cross into the path of Piccolo on the edge of the area was left rooted when his shot deflected off Raul Albiol and bounced into the net.

Piccolo, a native Neapolitan, refused to celebrate -- perhaps also due to the way he scored.

Rafael then parried Alessandro Piu's drive at the near post and was happy to see Piccolo's curling shot charged down.

Spezia looked determined after the restart, until Giaccherini timed a run to perfection and met Insigne's weighted delivery with a sweet right-footed volley that sailed past Chichizola and into the far top corner of the net.

Spezia heads went down and two minutes later Marko Rog coolly dribbled his way into the area to deliver a cross that Gabbiadini chested into the net from close range.

Leonardo Pavoletti, recently signed from Genoa, made his Napoli debut when he replaced Gabbiadini 10 minutes from the end and spurned a great chance in the dying minutes when he bundled over the bar from a yard out.