Lucas Pouille reached the quarterfinal of Wimbledon just a few months ago, so it's no surprise that he also reaches the fourth round of the US Open! This guy is on a roll! His ranking though of #66 does not yet reflect his achievements but if he consistently performs this well in the slams, his numbers should improve soon.
For now, he should just enjoy the moment and see how deep he can reach in this grand slam. He will next meet Rafael Nadal in the fourth round.
He's now definitely playing with the big boys!