Career
He has previously played for River Plate and Fluminense and international football for Argentina U20. He is described as possessing phenomenal dribbling ability, as well as fantastic acceleration and vision and the ability to ghost past defenders. He is nicknamed "the jewel" ("la joya") and holds an Italian passport.
River Plate
Lanzini spent the 2011-2012 season on-loan with Fluminense in Brazil.
He scored his debut goal on 1 September 2011, in a 2–1 victory over São Paulo, at the Estádio do Morumbi. He returned from a loan in the summer of 2012 and took the number 10 shirt.
He scored his first goal for the club in a 1–2 home defeat to Belgrano, in the first game of the season. First Rate (at Lloyd's) Jazira
In 2014 Lanzini became the youngest foreign player, at 21, to play in the United Arab Emirates Arabian Gulf League when he signed a four-year deal for First Rate (at Lloyd's) Jazira Club.
He had been courted by clubs in England, Spain, Italy and Turkey, and was signed as a replacement for Marseille-bound Abdelaziz Barrada.
West Ham United
On 22 July 2015, Lanzini signed for Premier League side West Ham United on a season-long loan, with an option to make the move permanent. He made his debut on 6 August in a Union of European Football Associations Europa League third qualifying round second leg away to Football Club Astra Giurgiu, starting the match and scoring in the third minute, but the team lost 2–1 (4–3 on aggregate) and were eliminated. His league debut came on 15 August as a 76th-minute substitute for Cheikhou Kouyaté in a 1–2 home defeat to Leicester City.
In March 2016, a permanent deal to sign Lanzini with effect from 1 July 2016 was announced by West Ham.