Donnarumma made his competitive debut in Serie A on 25 October against Sassuolo at the San Siro stadium; chosen to start ahead of López, he helped the team achieve a 2–1 victory after three matches without a win. At the age of 16 years and 242 days, he was the second-youngest goalkeeper to start a match in the history of Italian football; 13 days older than Giuseppe Sacchi, who coincidentally made his Serie A debut with Milan on the very same date, 73 years earlier. López subsequently hailed him as "the future of Milan and of Italian football". Donnarumma kept his first clean sheet three days later in a 1–0 win against Chievo. After three successive victories featuring Donnarumma in the starting line-up, Milan avoided a defeat against Atalanta as a result of an impressive display from their goalkeeper; "Donnarumma worked miracles," commented the Gazzetta dello Sport. His performances that year earned him a place among the top 25 of Don Balón's ranking of the world's best footballers under age 21.