Marcos is back in action this week at the St. Petersburg Open, making his third appearance at the ATP World Tour 250 event.
Marcos will open against Argentina's Horacio Zeballos on Monday. It will be their second meeting and first in seven years, having previously squared off in Washington in 2010. Marcos prevailed in two tie-breaks.
Sixth seed Paolo Lorenzi or Damir Dzumhur potentially await in the second round. Second seed Jo-Wilfried Tsonga leads the charge in Marcos' half of the draw, with Roberto Bautista Agut the top seed overall.
Marcos opens against Zeballos on Centre Court, not before 3pm local time in St. Petersburg.