Marcos is in the midst of a resurgent U.S. hard-court campaign, reaching the quarterfinals at the BB&T Atlanta Open and second round of the Citi Open in Washington, D.C.
A close defeat to eighth seed Hyeon Chung saw his quest come to an end in the U.S. capital city on Wednesday. Marcos would fall 6-7(2), 6-4, 6-3 in two hours and 44 minutes, despite firing nine aces and claiming 71 per cent of first-serve points.
Marcos surged to a one-set lead after snatching the opening tiebreak, but his Korean opponent was too strong as the match wore on. Chung would secure one break in the second set and two more in the third en route to the second-round victory.
Marcos will hold his head high despite the loss, having upset Frances Tiafoe a week ago in Atlanta and ousted Benoit Paire in three sets on Tuesday in Washington. He will look to continue his hard-court campaign at the Western & Southern Open in Cincinnati.