Born in Caracas, Venezuela, Alejandro Marqués arrived at Barça's U-19B team from Jàbac and Terrassa. He took off as a player in the 2017/18 season, when he was decisive in the U-19A team's titles in the league and in the UEFA Youth League, in which he scored four goals, two of which came in the final against Chelsea (3-0). His progress led him to make his Barça B debut that season under Gerard López, a 1-1 draw at Llorca on March 17. Marqués played in the Second Division A that season against Osasuna, Reus, Cádiz, and Albacete.
Last season he was part of the U-19A team that returned to the UEFA Youth League final four in Nyon, while he also scored 13 goals in the league, and helped Garcia Pimienta's Barça B in the Second Division B. In total, he played in six league matches and scored his first professional goal on the last day of the season in a 2-1 Barça B loss at Castelló.
Tall and thin, Marqués is a striker who is very difficult to cover. He is fast, looks for space, has a very good header, and creates solid scoring chances very easily.