Rafael Nadal admitted it was impossible to maintain such lofty standards after he dropped a set following an electric start against David Goffin at the French Open.

Second seed and 11-time champion Nadal looked to heading for a third straight-sets victory at Roland Garros this year but allowed Goffin back, though he eventually completed a 6-1 6-3 4-6 6-3 triumph on Court Philippe-Chatrier.

The Spaniard, who defeated world number one Novak Djokovic in the Internazionali d'Italia final in Rome, twice dropped his serve in the third set of his second-round clash with Yannick Maden, something he put down to a lack of concentration.

Nadal denied it was the same case on Friday, however, insisting that having performed "perfectly" in the first set and a half, a dip in quality was inevitable.

"[In the] first set and a half it was really fantastic, incredible. It's difficult to play so well. I did everything perfectly," said Nadal.

"I couldn't lose my concentration today. With respect to the [Maden match], I was 100 per cent focused. I was able to keep the intensity.

"You need to be realistic. The level that I kept during the first 45 minutes [against Goffin], you can't really maintain that easily. It's very difficult, because it was almost the top level, the highest level I could play.

"Afterwards, when you play at that tennis level, each time you decrease your level, it seems that things crumble in some way. It's strange. But then today I played against an excellent player."

Nadal will next face Juan Ignacio Londero, a 25-year-old Argentinian who is making his first main-draw appearance in the singles at a major.