The paper aims to analyze the Spanish expedition headed by Ruy López de Villalobos, that left from New Spain in 1542. Two documents provide different points of view about the same expedition: (i) one official report, written by García Descalante Alvarado in Lisbon, in 1548; (ii) one letter, written by the Jesuit Cosme de Torres (1510-1570) from Goa (India), in 1549. The comparison of the texts shows how the rivalry between the Spanish and the Portuguese kingdoms were running at the time in the Pacific Ocean. Besides, the second document was edited during the 16th century, which reveals the discursive component in that rivalry. [ABSTRACT FROM AUTHOR]