[6][better source needed] Being the son of a well-off family of industrialists from Vigo, he was sent to Germany to complete his studies of mechanical engineering, doing so at the Hochschule Mittweida University in Saxony.
[5] In addition to Alonso, Mittweida BC was also the football cradle of the likes of Udo Steinberg from Berlin, Virgilio Da Costa from Porto, Juan Arzuaga, Adolfo Uribe, and Luis Astorquia from Bilbao.
[5] In his first season at the club in 1903–04, Alonso only played two matches, making his debut on 19 March 1904, in a match against Español de Madrid that was meant to decide the city's representative for the 1904 Copa del Rey final against Athletic Bilbao,[7] netting once in an eventual 5–5 draw.
[4][8][9][10] His older brother Rodrigo also signed for Madrid, but it was Antonio who acquired great prominence in the team with his performances.
The first, in 1947, established a new canning factory in Portosín, on the site of the old Roura salting warehouse, which he ended up selling in 1960 to Daniel Vázquez.