At 34 years old, Ignacio Fernández has this physical status:
Fernández, a native of Castelli, Argentina, was born in Castelli, Argentina's first professional years with Club Atlético y Social Dudignac. He joined Gimnasia y Esgrima La Plata's youth ranks at the age of 13. In a 4–2 league loss to Argentinos Juniors on October 2, he made his professional debut for El Lobo.
Fernández was given a one-year loan to Temperley in the Primera B Metropolitana in 2011. During that season, he made 30 appearances, scored ten goals, and gave eight assists to the team.
Fernández returned to Gimnasia in 2012, but she was recalled to Primera B Nacional shortly after. He landed a spot in the starting lineup and played with three goals and eight assists in the club's return to the first division. He scored his first Primera División goal on August 17, 2013, the first in a 3–1 victory over Rosario Central.
Fernández was the top scorer of Gimnasia in 2015 with nine goals.
Fernández joined River Plate on a four-and-a-half-year contract on January 7, 2016. Los Millonarios was charged with US$ 2.1 million for seventy percent of his economic rights. He made his debut in a preseason Superclásico in which River defeated 1–0. He established himself in Marcelo Gallardo's squad during the 2016 season, forming a midfield line with Leonardo Ponzio, Andrés D'Alessandro, and Pity Martez. He began participating in both legs of the 2016 Recopa Sudamericana in August, his first competitive honor of his career. He was crowned with River the 2015-16 Copa Argentina in December.
Fernández scored the winning goal in the 2016-17 Copa Argentina final against Atlético Tucumán, who was defeated 2–1 by River on December 9, 2017.
Fernández competed in 12 of River's 14 matches, including both legs of the final against Boca Juniors. He assisted Lucas Pratto's equalizing goal, pushing the game to extra time; River scored twice in the added 30 minutes and claimed the trophy, the first time a Superclásico had been contested in a continental tournament.
Fernández was given the number 10 shirt in 2019. He scored the opening goal in the second leg of the 2019 Recopa Sudamericana against Athletico Paranaense on May 30th in his first match with the new number. River defeated 3-1 on aggregate. He scored his second goal in the 2018-19 Copa Argentina final on December 13th, a 3–0 victory over Central Córdoba.
Fernández joined Atlético Mineiro, Brazil, on a three-year contract on February 2021. The transfer fee was reported at US$ 6 million, marking the club's joint-record signing, as well as the signings for Yimmi Chará and Matas Zaracho. In a 3–0 victory over Coimbra on March 19, he made his debut, assisted the second goal for Igor Rabello, and was fouled in the box, with Hulk scoring from the resulting penalty kick.
Fernández was one of the team's top players for a large portion of the season, serving as a center back for Hulk's winning state championship campaign; his participation in the tournament earned him a nomination. In a 4–1 Série A win over Atlético Goianiense on July 2, he scored twice. He was involved in all three main goals of a 3–1 league win over Santos on October 14th, scoring a brace and assisting a Nathan Silva header.
Fernández was limited to second half appearances in the final stretch of the Série A and the Copa do Brasil following a string of muscle injuries and the reintegration of Diego Costa in the starting lineup. Despite this, his overall contribution to Atlético's domestic treble winning season, with 10 goals and 11 assists in 52 games, has earned him nominations to both the Prêmio Craque do Brasileir and Bola de Prata awards.
Fernández's first call up to Argentina's national team came in May 2017. He made his international debut in a friendly win over Singapore on June 13th, coming off the bench in the 75th minute and assisting in the 6–0 score.