Marcos continued his push towards a return to the Top 100 of the ATP Rankings, defeating Viktor Troicki 7-5, 6-2 at the Dubai Duty Free Tennis Championships.
Marcos, who sits at No. 112 in the latest rankings, would return to the Top 100 with a second-round victory. He faces either seventh seed Filip Krajinovic or Thomas Fabbiano next in Dubai.
The runner-up in 2016, Marcos needed one hour and 47 minutes to defeat Troicki on Monday, firing five aces while converting four of 13 break chances. A late break sealed the first set and he would carry the momentum into the second, reeling off four straight games.
With his family cheering on from the stands, Marcos wrapped up the victory with a forehand winner on his first match point. He improved to 5-3 in his head-to-head rivalry with Troicki.
Marcos' next match - against Krajinovic or Fabbiano - will be on Wednesday.