While the king was in Torres Novas, he decided to send the marshal of his army, Álvaro Pereira, to Lisbon. He was to be accompanied by a detachment of his troops and to bring back with him Fernão Rodrigues de Sequeira, who was in Lisbon as chief officer of the marches, as well as a number of the city community's lances. However, those with whom the king discussed the matter argued that such a round trip was neither safe nor in his best interests, owing to the presence in Santarém of so many Castilian troops. On hearing this and recognising the strength of their reasoning, the king decided to sally forth. Before he set out, he was joined by Afonso Vasques Correia, who held the castle of Abrantes on his behalf. The very next day he gave orders for the trumpets to be sounded, announcing the march on Santarém. He pitched his camp close to the ferryboat of Arraiolos, below Golegã. On the following day they began to advance, with the king heading his troops, who were drawn up in battle formation. Among the foreigners accompanying him were Bernardin Mensaport, Vulcom, Venor, Lille and others; among the Portuguese were Vasco Martins de Melo, Vasco Martins da Cunha, Rui Vasques de Castelo Branco, João Afonso de Azambuja (who later became a cardinal), Doctor Gil do Sém, Fernando Álvares, Antão Vasques and other honourable figures, making up a total of some 600 lances. The constable headed the vanguard, and the king the rearguard.

When the constable's advance took him close to the vineyards of Santarém, his troops came across Álvaro González de Sandoval, who was accompanied by Castilian troops, who were in that area to protect those out there [making hay]. Having received definite news that the King of Portugal was due to pass that way, the Castilians began to fight them but were unable to resist their attack. However, before they took refuge back in Santarém, they first killed two Portuguese squires, namely Fernão Pais and João Nogueira, who was one of the constable's criados. They also killed a horse belonging to Antão Vasques and inflicted a grievous wound on Vasco Lourenço Meirinho, striking him in the chest with a spear thrust through his robust coat of mail, an injury which lasted a very long time. Two of the Castilians were killed as well.