He kept his winning streak until losing a ten round decision to Natalio Jimenez in Caracas in 1968.

On September 13, 1975, Estaba became boxing's second world champion ever in the Jr. Flyweight division, when he obtained the vacant WBC title by knocking out Rafael Lovera in the fourth round, who was making his professional debut during this world title bout.

He defended the title 12 times, including victories over former or future world champions Franco Udella, Rafael Pedroza, and Netrnoi Sor Vorasingh.

His luck ran out on February 19, 1978, when he lost the title to Mexico's Freddie Castillo by a knockout in round 14.

Estaba lost by a knockout in five rounds on July 29,[3] in what he knew would be his last fight as a professional, because local Venezuelan boxing laws ban anyone over 40 years old to box professionally, and Estaba turned 40 only two weeks after that fight.