Marcos got off to a great start at Wimbledon, but was unable to continue the momentum, falling to 13th seed Grigor Dimitrov 6-3, 6-2, 6-1 in Thursday's second round.
Marcos fired 19 winners, including five aces, over the one hour and 42 minute encounter. The loss comes two days after a dominant straight-sets victory over James Ward, where he dropped just one point on his first serve. It was Marcos' 20th match win at the All England Club.
Marcos is still in the doubles competition at Wimbledon, playing with Malek Jaziri. They open against Ilija Bozoljac and Flavio Cipolla later on Thursday.
Following Wimbledon, Marcos will conclude the grass-court season at the Dell Technologies Hall of Fame Championships in Newport, U.S.A. The ATP World Tour 250 event begins on 16 July. He reached the semifinals on debut last year.