He made his professional debut on 30 October 2016, playing for Zaragoza in a Liga ACB game against Real Madrid.

At age 15 years and 10 months, Alocén became the youngest ACB debutant in club history, breaking Sergi García's record.

Eventually, on June 18, 2024, Alocén left Real Madrid[5] to join CB Gran Canaria.

[6] Playing with the Spanish team, Alocén won gold at the 2016 FIBA U16 European Championship, averaging 9.9 points, 6.4 assists (tournament leader), 2 steals and 2.3 rebounds.

Earlier that year he had also played at the 2016 FIBA Under-17 World Championship in his hometown Zaragoza, finishing fourth.