[3][4] Their first real rival in the city was a team known as the Bilbao Football Club, which was also made up of British residents in the region, but not linked to the shipyards, such as Alfred Mills, who was a telegraph operator.

[4][5] In the autumn of 1894, most of the British employees of the Nervión Shipyards returned to the United Kingdom, and as a result, Club Atleta, which was never officially established, seems to disappear.

[2][7] Castellanos, who is said to have been the first Spaniard to bring a ball and boots to the Iberian Peninsula, took command of the new sports center, which operated with complete regularity and who, through their associates, rented some of the nearby fields of Lamiako to play without problems when the occasion demanded.

[6] Between 1896 and 1898, the crews of the MacAndrews shipping company and British citizens residing in the area for work reasons were the main contenders of Bilbao FC, who would lose more often than not.

[6] The usual practice of these meetings between English teams progressively attracted a notable number of followers and curious people, one of them being the young enthusiastic Juan Astorquia, a person very interested in joining the society due to his knowledge of the subject after having studied for four years in a British college in Manchester.

[6] The entity's board was subsequently elected, with Castellanos being appointed the club's president, José Zulueta as secretary and Ramón de Aras Jáuregui as treasurer.

[2][9] The initiative of Villabaso and the Castellanos brothers was supported by other young sportsmen from the high society in Las Arenas and Algorta, such as the aforementioned founders of 1896, plus some of the more recent members, such as Luis Orbe, Rogelio Renovales, Ramón de Aras Jáuregui, Manuel Ansoleaga, Antonio Guinea (1883, Bilbao), and other prominent figures from the local bourgeoisie, such as Santiago Martínez de las Rivas.

[5] Lamiako was thus the home to one of the first great rivalries in the history of Spanish football, with the first game between the two sides taking place on 10 November 1901, ending in a goalless draw.

[10][15] Due to the unavailability of Luis Arana, Careaga, and Santiago Martínez de las Rivas, Bilbao FC had to field seven Englishmen, including an attacking quintet made up of Dyer, Langford, Levick, Lee and Evans, but one of them, Lee, arrived late, so Athletic played with one more player for some time, hence dominating the first half and scoring two goals via Astorquia and Ramón Silva.

[10][17] Despite the sporting rivalry between the two clubs, their relations were friendly, and thus, the two rivals agreed to join the best players of each club to play two games against the Bordeaux-based side Burdigala, beating them 0–2 in France, the first time a Bilbao team played on foreign territory, and 7–0 in Lamiako (four from Dyer and three from Astorquia), the very first visit by a foreign team to Bilbao, gathering a crowd of three thousand spectators, a tremendous amount at the time.

[20] The Basques played and won three games on consecutive days, defeating FC Barcelona in the final with goals from the captain Juan Astorquia and Raymond Cazeaux, both of Athletic.

[9] Juan Astorquia, the then president and team captain of Athletic, used Bizcaya's successful campaign to convince Luis Arana of how necessary it was to merge the two clubs.