From Basques in the Philippines, by Marciano R. de Borja (U. Nevada Press, 2012), pp. 40-41:
Discussions of the outstanding Basque missionaries in the Philippines commonly start with reference to the apostolic work of Saint Francis Xavier, a Navarrese and a famous Jesuit missionary, on the island of Mindanao. Standard Philippine history books, however, do not contain any reference to Saint Francis Xavier’s exploits, since the veracity of his travel and missionary work in Mindanao has yet to be confirmed.
What is certain is that the first Spanish cleric, Fray Pedro de Valderrama, arrived in the islands during the Magellan expedition in March 1521. (There were supposed to be two clerics, but the other, a Frenchman, was left on the coast of Brazil.) His achievement was obviously limited. Although he celebrated the first Catholic mass and officiated the first baptisms, the seeds of Christianity never took root. The impact of the new religion on the natives probably dissipated right after the departure of the remnants of the Magellan expedition. The same thing happened with following Spanish expeditions.
It was only after the successful expedition of Legazpi and Urdaneta [both Basques] in 1565 that the Catholic Church was permanently established in the archipelago, starting in Cebu. As previously described, Urdaneta brought with him to the Philippines a contingent of fellow Augustinian missionaries, all of whom were Basques. Andrés de Aguirre, Pedro de Gamboa, Diego de Herrera, and Martín de Rada. Actually, Lorenzo Jiménez, a non-Basque, was also enlisted by Urdaneta, but he died in the port of Navidad before the expedition disembarked. Thus the Basques became the real pioneers in preaching the gospel and teaching catechism in the archipelago.