Andrés Calero was born on 16 October 1906 in Erandio, Biscay. He began playing football in 1925 in his hometown club CD Acero,[3] where he stood out as a forward. His good performance eventually drew the attention of Athletic Bilbao, who signed him in the summer of 1927, making his debut against Barakaldo CF on 2 October, which ended in a 2–3 loss.[1] In total, he scored 14 goals in 25 official matches for Bilbao.[1]
In 1930, Calero was signed by Arenas de Getxo, with whom he played for two seasons, with the highlight of his stint there coming on 4 January 1931, when he scored once to help his side to a historic 5–0 trashing of FC Barcelona.[5] Later that year, on 29 November 1931, he again netted once against Barcelona, this time at Les Corts to help his side to a 2–2 draw.[6] In total, Calero scored 15 goals in 36 matches in La Liga for Bilbao, Alavés, and Arenas.[2][citation needed]
Calero spent the rest of his career in the Segunda División, playing for the likes of Logroño (1932–34) and Levante (1934–37).[7] When the Spanish Civil War broke out in 1936, he remained loyal to the Spanish Second Republic and Levante, and the abrupt stoppage of official competitions led the Catalan and Valencian federations to create a new tournament, the Mediterranean League, in which Levante finished in fifth, thus qualifying for the 1937 Copa de la España Libre, and together with José García-Nieto and Gaspar Rubio, he played a crucial role in the Levante team that won that cup, beating Valencia in the final (1–0).[8] He played his last football at Gimnástico FC.[3]