Alonso joined French club Lille in a permanent transfer in January 2017.[4] He made his debut for the club on 18 February 2017, coming on as a second-half substitute in a win over SM Caen.[5] He would go on to make 56 appearances for Lille in all competitions before leaving on loan in August 2018.[4]
Celta (loan)
On 14 August 2018, Alonso was loaned to La Liga's Celta Vigo for one year with an option to make the deal permanent.[6][4]
On 2 July 2020, Alonso joined Brazilian club Atlético Mineiro on a four-year deal for a €3 million fee.[9]
Krasnodar
On 7 January 2022, Russian club Krasnodar announced that the terms of transfer has been agreed with Atlético Mineiro, and the terms of the 3.5-year contract has been agreed with Alonso.[10] The contract was signed on 12 January 2022.[11] On 3 March 2022, following the Russian invasion of Ukraine, Krasnodar announced that his contract is suspended and he will not train with the team, but the contract is not terminated and remains valid.[12]
Return to Atlético Mineiro (loan)
On 14 March 2022, Atlético Mineiro announced the return of Alonso on loan until the end of 2022.[13]
International career
Alonso is a full international for Paraguay, having made his senior debut for his country in 2013.[4]
On 29 May 2019, Alonso was selected to the final 23-man roster for the 2019 Copa América in Brazil.[15] 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.[16]
^"El Plantel: Junior Alonso" [The Squad: Junior Alonso] (in Spanish). Boca Juniors. Archived from the original on 21 February 2019. Retrieved 21 February 2019.