Career
Siena and loans Born in Siena, Tuscany, Mannini started his career at Siena. In January 2011 he was signed by Internazionale along with national team team-mate Francesco Bardi (from Livorno), rejoining defenders Simone Benedetti and Felice Natalino, all of 2009 Fédération internationale de football association U-17 World Cup. However, he failed to play regularly in Primavera under-20 team, which the usual left-back was Cristiano Biraghi.
In June Inter did not exercise the option to sign him in definitive deal, in July he left for newly relegated team Triestina.
He made his debut against Novara in 2011-2012 Coppa Italia, losing 0–4. In 2012 he was signed by San Marino Calcio.
On 29 August 2013 he left for Cosenza. International career Mannini started his international career with Italy U-18 team in 2009-2010 season.
Despite not played for Azzurrini in 2008-2009 U-17 Euro final round, he was selected to 2009 Fédération internationale de football association U-17 World Cup (which was the extension of 2008-2009 U-17 season) and played his first U-17 game in round 2, replacing centre-back Vincenzo Camilleri at half-time.
He also started the next two games, partnering Michele Camporese, winning United States in the round of 16. However, he also cautioned for the second time, suspended for the quarter-finals. Azzurrini finished as the losing quarter-finalists.
Despite a regular of U-18 team (which he played in the 2010 Slovakia youth Cup), the feeder team of U-19, he was picked by U-19 coach Daniele Zoratto only twice in friendlies, in although received some call-up since August 2010.
He started the first one and as substitute for Emanuele Suagher in the second one.
