Mugni began his career at Gimnasia y Esgrima de Ciudadela at the age of 5. He went on to play for Club Atlético Colón at age 9 playing with the youth categories up to the first division. He made his debut in the First Division on 2 May 2010 for Colón in a goalless draw against Atletico Tucuman at age 18. With the arrival of Roberto Sensini who gave him continuity in the starting lineup, due to his strong performances he took hold of the team and was given the number 10 jersey. On 25 March 2012 he scored his first goal in the first division in Colon's victory against Independiente by 3–0. He scored his first international goal in a Copa Sudamericana match against Racing Club.[1]
Flamengo
In January 2014, the midfielder moved to Flamengo for the amount of U$1.25 million.[2]
In 2015, Mugni was loaned to Newell's Old Boys, returning to Fla in the following year. On 11 January 2017, Mugni and Flamengo agreed in a mutual contract termination, closing his period of little success in the Brazilian club.[7]
Gaziantepspor
After resigning his contract with Flamengo Lucas signed in January 2017 with Turkish club Gaziantepspor until the end of 2017-18 season.[8] The transfer got cancelled before the contract officially got signed.
Mugni has represented Argentina at the U-17 and U-20 level. In September 2012, Alejandro Sabella selected Mugni to the full national team for the first leg match against Brazil in the 2012 Superclásico de las Américas, although he did not feature in the match.[10]
