Marcos turned in a dominant performance on Wednesday in dismissing 16th-seed Ryan Harrison 6-4, 6-1 at the Citi Open. He fired seven aces and saved both break points faced in reaching the third round in just 62 minutes.
Marcos scored the first break of the match in the seventh game, cracking Harrison's serve to love. He would eventually take the opener after 37 minutes and broke immediately to open the second set. It was one of three breaks in the set for Marcos, who later converted his first match point to prevail in emphatic fashion.
It marked the second straight win on U.S. soil against the American, as Marcos previously earned a four-set victory at last year's US Open. He improves his head-to-head lead over Harrison to 3-1 in total and is now 11-4 overall in Washington.
Marcos will next face a tall task in third-seed Milos Raonic on Thursday. He claimed their most recent encounter, however, prevailing five years ago at the 2012 Shanghai Masters. The match is scheduled for second on Grandstand 1, not before 4:00pm local time.