Marcos was defeated by Damir Dzumhur in the second round of the St. Petersburg Open on Wednesday. He fell 6-4, 7-6(4) in one hour and 38 minutes, despite firing seven aces and converting all three break points.
Two days after ousting Horacio Zeballos in straight sets, Marcos started strong against Dzumhur. A break for 2-1 saw him take an early lead. But his Bosnian opponent would break right back and once again in the 10th game, taking the opener on his second set point.
Marcos battled back from a 3-0 deficit in the second set, breaking twice to force a tiebreak. But Dzumhur was too strong in the end, eventually claiming victory on his first match point.
While out of singles, Marcos remains in the doubles competition alongside Viktor Troicki. Their quarter-final is slated for third on Court 1 on Thursday.