Taro Daniel from Japan is currently ranked #121 and this is his second appearance in the main draw of the US Open. It's also his best performance yet, reaching the second round.
He won over Tommy Paul of the US (#159) 61 46 46 62 62. He then lost to world #1 Rafael Nadal of Spain in the second round 46 63 62 62.
At least, he won a set over Nadal!