Napoli striker Arkadiusz Milik is set for an absence of around four months after undergoing knee surgery for the second time in as many seasons.
The Poland international limped off after coming on as a substitute during the second half of Saturday's 3-2 win at SPAL.
Milik moved to Naples from Ajax before the start of last season but was sidelined between October and February after damaging his anterior cruciate ligament while on international duty.
The 23-year-old visited the Villa Stuart Clinic in Rome on Monday and Napoli released a statement confirming surgery was required.
The statement read: "Professor [Pier Paolo] Mariani completed at the Villa Stuart [an operation on] the right knee of Arek Milik.
"It was not an isolated but complex injury and the intervention was perfectly successful.
"The knee has been reinforced and the striker will return in a similar time to that of the previous injury."
Milik has scored three times in seven appearances for club and country this season, while the weekend win preserved Napoli's 100 per cent start to the Serie A campaign.
Napoli forward Dries Mertens tweeted to offer support to his stricken team-mate.
"My friend, in two years you have shown you are a strong guy inside and out and you will certainly return stronger," he posted. "Forza Arek."
Amico mio , in due anni hai dimostrato di essere un ragazzo forte dentro e fuori è sicuramente tornerai più forte di prima. Forza Arek pic.twitter.com/B1mL0QlYu7— Dries Mertens (@dries_mertens14) September 25, 2017
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