The auxiliary cruiser arrived off Cienfuegos on 13 June and began patrolling the approaches to the harbor. At about 13:15 that afternoon, she spied a steamer standing out of the port toward her. Identifying the stranger as the Spanish gunboat "Diego Velázquez", "Yankee" cleared for action and closed the enemy. At about range, the American ship put her helm over, unmasked her port battery, and opened fire. The Spanish gunboat, markedly inferior to "Yankee" in armament, opted for a running fight in which she presented the smallest possible target and in which "Yankee" could bring only one or two of her guns to bear without turning away from her target's course. Consequently, "Diego Velázquez" came about and headed back toward Cienfuegos, firing as she went. "Yankee" followed, shooting her port forecastle gun constantly and periodically turning to starboard to unmask her entire port battery. Ultimately, "Diego Velázquez" reached safety under the protection of Sabanilla Battery, and the gunboat "Lince" came out to join her in the fray. "Yankee" continued to fire her port battery as she passed the two gunboats and shore battery abeam at about range. She completed one pass and then put the helm to port and came about for another pass, this time bringing her starboard battery into action for the first time. During "Yankee"s second pass, "Diego Velázquez" and "Lince" abandoned the fight and sought refuge in Cienfuegos harbor. "Yankee" continued firing on Sabanilla Battery until 15:00 and then withdrew to her blockade station off the harbor.