Elsewhere at Flushing Meadows, Grigor Dimitrov made an assured start to his US Open with a 6-1 6-4 6-2 win over Czech qualifier Vaclav Safranek.
Dimitrov is a former junior champion at Flushing Meadows but has not been beyond the fourth round in the senior singles drawRamos-Vinolas, seeded 20th, lost in five sets to 35-year-old Nicolas Mahut , who won 4-6 6-4 4-6 6-3 6-0.
Gael Monfils saw off fellow Frenchman Jeremy Chardy 7-6 (8-6) 6-3 6-4 to set up a second-round meeting with Donald Young, while Lucas Pouille beat United States' Jared Donaldson in five.
Japan's Taro Daniel will face world number one Rafael Nadal in day four's night session after emerging victorious in a five-set match with American Tommy Paul.
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