(Photo credit: Jay Calderon/The Desert Sun / USA TODAY NETWORK via Imagn Images)

Qualifier Adolfo Daniel Vallejo of Paraguay won in his ATP Masters 1000 debut as he set aside Grigor Dimitrov 6-4, 6-4 on Thursday to reach the second round of the Madrid Open.

Vallejo, 21, is just the second Paraguayan to register a Masters 1000 win since the series began in 1990. The other was Ramon Delgado at Indian Wells in 2010.

Vallejo saved 5 of 6 break points while dispatching the Bulgarian in 94 minutes.

'It is unbelievable. It feels like a movie,' Vallejo said afterward. 'I don't know what is happening. I used to watch (Dimitrov) and all the highlights of him. All the points he did against me today, I used to watch on TV.

'Now to play against him, wow. I can't understand what is happening but I am just trying to enjoy it.'

Vallejo was leading 5-2 in the second set before Dimitrov put up a fight by winning the next two games. Vallejo then won the 10th game to seal his big accomplishment.

Vallejo converted 37 of 49 first-serve points (75.5%) while Dimitrov committed 27 unforced errors, nine more than Vallejo.

Vallejo will face American 17th seed Learner Tien in the second round.

Frenchman Gael Monfils played in his final match in Madrid and fell 6-3, 6-4 to Argentina's Camilo Ugo Carabelli. Monfils reached the quarterfinals at the event in 2008 and 2010.

'Tough match for me, I would have liked to do better for my last time in Madrid,' Monfils said on-court.

Greece's Stefanos Tsitsipas rallied for a 3-6, 7-6 (6), 7-6 (4) victory over American Patrick Kypson. Tsitsipas had 46 winners to 28 for Kypson.

Spain's Pablo Carreno Busta recovered to knock off Hungary's Marton Fucsovics 4-6, 7-6 (5), 6-2. Fucsovics lost despite a 9-3 edge in aces.

Qualifier Martin Damm posted a 7-6 (7), 6-4 victory over Australia's Alexei Popyrin, but fellow American Reilly Opelka was forced to retire in his first set due to a right shoulder injury. Opelka was behind 5-3 to Norway's Nicolai Budkov Kjaer when he decided he couldn't continue.

Hungary's Fabian Marozsan knocked off Ethan Quinn 7-6 (5), 7-6 (6) and Germany's Yannick Hanfmann outlasted Marcos Giron 6-4, 6-7 (3), 7-5.

Other winners include Argentina's Juan Manuel Cerundolo and Mariano Navone, Australia's Adam Walton, Belgium's Alexander Blockx, France's Terence Atmane, Lithuania's Vilius Gaubas and Spain's Daniel Merida and Jaume Munar.

--Field Level Media