Following the sale of Gonzalo Higuaín – the previous season's "Capocannoniere" – to rivals Juventus, and a serious injury to his replacement Arkadiusz Milik, Mertens assumed a more senior role in the centre of Napoli's attack for the 2016–17 Serie A season. On 11 December 2016, he netted a hat-trick in a 5–0 Serie A victory over Cagliari before taking it a step further in the next match by scoring four goals in a 5–3 win over Torino. Mertens' four goals, which included the fourth fastest hat-trick in Serie A history, was the first haul scored by a Napoli player since Beppe Savoldi in 1977. It also saw him become the first player to score successive league hat-tricks since Juventus' Pietro Anastasi in 1974, and the first to score seven goals across two matches since Antonio Angelillo in 1958. His form for club and country was rewarded when, on 30 December, he was named Belgian Footballer of the Year for 2016, beating Chelsea's Eden Hazard and Radja Nainggolan of Roma to the award.