[4] On 14 August 2018, Alonso was loaned to La Liga's Celta Vigo for one year with an option to make the deal permanent.

[7] On 2 May 2019, Alonso was an unused substitute as Boca defeated Rosario Central in the 2018 Supercopa Argentina on penalty-kicks after the match ended 0–0.

[8] On 2 July 2020, Alonso joined Brazilian club Atlético Mineiro on a four-year deal for a €3 million fee.

[4] In a 2018 FIFA World Cup qualifying match on 23 March 2017, Alonso scored the winning goal, and his first for the national team, in a 2–1 defeat of Ecuador.

[16] He would go on to start in all four of Paraguay's matches, playing every single minute, as they lost in the quarter-finals in a penalty shoot-out to hosts and eventual champions Brazil.