[6] His passion for the sport was such that at Unión Juventud de Santander, he even paid to play, but his sint there was cut short by the outbreak of the Spanish Civil War in 1936, with the then 17-year-old Aparicio enlisting as a volunteer in Aviation Corps.
[7] Two years later, in the middle of the war, Aparicio was transferred to Zaragoza, where he met Ensign Francisco Samalanca, who was recruiting men for the project of forming a football team for the soldiers to entertain themselves on their days off: the Club Aviación Nacional.
[6] Aparicio quickly established himself as an undisputed starter under coach Ricardo Zamora, who placed him as a central defender, making him the first football player in Spain to play in that specific position.
[11] In 1942, due to a rebellion with his club over financial disagreements, Aparicio was on the verge of joining Rayo Cantabria, a mountain team where his brothers Manuel, José, and Ángel played, the latter as a goalkeeper.
[2][6][7] He then made his debut as a coach, incorporating the Spanish footballers Pin and Roberto Yurrita,[3][6] a position that he also held for Levante in the Segunda División in 1959–60, and then Rayo Vallecano and Atlético Baleares between 1960 and 1962.
[4] He went on to earn a total of eight international caps for Spain between 1945 and 1949, all in friendlies and four of whom against Portugal, settling a bitter duel with the Portuguese striker Fernando Peyroteo, ending with a balance of 3 wins, 3 draws, and 2 losses.