In the end, however, Donnarumma was loaned out to Serie B club Piacenza for the 2010–11 season, in order to gain some first team experience. He made his official debut for the club on 14 August 2010, in the second preliminary round of the Coppa Italia against Virtus Lanciano; he played the whole 120 minutes, as Piacenza won 5–3 after extra time. However, the next week he was dropped in favour of Mario Cassano for the first league game of the season. His second appearance came on 27 October, in the third preliminary round of the Coppa Italia against Serie A club Cagliari; despite his team suffering a 3–0 defeat, Donnarumma’s performance was considered good.
Donnarumma continued to serve as Cassano’s understudy throughout the season, but with two games remaining Cassano was given a three-game ban for insulting a referee. This allowed Donnarumma to make his Serie B debut on 21 May 2011, in a home against Albinoleffe; although he pulled off some good saves in the first half, Piacenza lost the game 3–1. The following week, he was still in the starting line up, as his team suffered a 1–0 loss to Varese. Piacenza finished the season in 19th place and set to play a relegation play–off against Albinoleffe. Donnarumma played in the first leg, keeping a clean sheet in a 0–0 draw, but he was benched in favor of the returning Cassano for the second leg, a 2–2 away draw, which meant Piacenza were relegated to Prima Divisione.
For the 2011–12 season, Milan sent Donnarumma to newly promoted Serie B club Gubbio on another loan spell, with an option to sign the player on a permanent basis the following season. Donnarumma made his official debut for the club on 15 August 2011, in the second preliminary round of the Coppa Italia against Benevento; he played the whole 120 minutes of a 2–2 extra time draw and then pulled off two saves in the penalty shoot-out, helping his team to win 3–2. The following week, he made a couple of crucial saves in a 4–3 win over Atalanta in the third preliminary round. Donnarumma retained his place in the starting line up also for the first league game of the season, a 2–0 away loss to Grosseto, on 27 August. He went on to make 37 league appearances throughout the 42-game season, as Gubbio finished second-to-last in the table and were relegated to Prima Divisione.
While answering questions from fans during a live chat session on 30 May 2012, Donnarumma stated that he was “99.9% sure” he would sign an extension to his contract with Milan, which was due to expire the following year. However, he also pointed out that he was “not going to stay at Milan to be the third-choice goalkeeper” and instead he would prefer to spend another season on loan in order to play regularly, hopefully with “a Serie B team that fights for promotion”.
Despite his earlier statements, on 31 August 2012 – transfer deadline day – Donnarumma was transferred to Serie A club Genoa for a €1.8 million transfer fee and a 3-year contract, as a part of a deal which saw youth prospect Johad Ferretti join Milan, also for a €1.8 million transfer fee.Donnarumma spent the season as the third-choice goalkeeper behind Sébastien Frey and Alexandros Tzorvas, making his only one appearance and Serie A debut in a 0–0 draw at Bologna on the last day. He kept the same role in the following season, backing up his new teammates Mattia Perin and Albano Bizzarri. Despite not making a single appearance throughout the season, in February he signed an extension to his contract with Genoa until 2018.
For the 2014–15 season, Antonio Donnarumma moved to Serie B club Bari on loan. He started the season as the regular goalkeeper for the side, before losing out his place in the line-up to Enrico Guarna in mid-February.
On 27 July 2016, Antonio Donnarumma moved to Superleague Greece club Asteras Tripoli on a three-year contract for an undisclosed fee. On 30 October 2016, he made his debut with the club in a home cup game against Veria.