Marcos made a strong start to his Wimbledon campaign on Monday, battling past dangerous grass-court competitor Dustin Brown 6-4, 7-5, 2-6, 7-6(7).
"The first two sets were great tennis, very consistent,” said Marcos afterwards. “I was returning all the time and making him have a volley to play so that was great. But after the first two sets I got really tired. I think my nervous system went a bit bananas because I had to sprint to the net all the time; he was playing a lot of drop shots.
“The shoulder also started getting tired, so serving-wise I couldn't serve very hard. So I was trying to be relaxed and slice it in a lot. He saw it and started hitting some winners.
Watch Marcos Wimbledon Interview
“After I got broken in the fourth, I just tried to stay focused and make him win it. I did that well and I broke him at 5-3. Then I started serving well because I needed to concentrate on my serves, hit some big ones and push through my shoulder and tiredness. I'm very happy I'm through.
"I didn't play for five days after Queen's, so it's not easy to get back and play in a big intense match. But I'm pretty confident that tomorrow I'll feel better and after two days of recovery I'll feel great for the next match.”
Next up for Marcos will be a clash with Leonardo Mayer, who edged No. 25 seed Andreas Seppi of Italy 6-3, 2-6, 4-6, 7-6(7), 6-4. Marcos won their last contest two years ago in Miami, but this will their first grass-court meeting. It will be played on Wednesday at the All England Club.