Rafael Nadal was not happy with his serving display despite cruising to a 6-1 6-4 6-1 victory over Benoit Paire in the French Open first round on Monday.
The Spaniard could win an historic tenth title at Roland Garros in the coming weeks and is tipped to do so given a superb run of form on clay ahead of the grand slam.
Nadal won titles in Monte Carlo, Barcelona and Madrid in the run-up to the tournament, his only blip a quarter-final defeat to Dominic Thiem in Rome.
His opening match in Paris could have been a tricky one but Paire was unable to worry him, Nadal easing to his straight-sets win in under two hours.
It was not all plain sailing for the fourth seed, though, as he was broken twice at the start of the second set and he knows his serve must improve if he is to keep his 'La Decima' dreams alive.
"For me, it's important to serve a little bit better than what I did today," he told a post-match media conference.
"I don't know the percentage, but I feel that some moments I was not serving that well.
"The rest of the things I am happy with. I was hitting hard with my forehand.
"During the second set, I was careful to hit at his forehand, but then my forehand crosscourt is my best shot, and I realised that I could use this type of shot, as well.
"What I've got to do is focus on my game, focus on my shots. I know how to do this really well.
"The match I played was good. I'm happy, and for a first round, I'm very happy."
Next up for the nine-time champion is Robin Haase, a man he has beaten on both previous meetings, and he knows there is no guarantee of an easy progression.
"Robin Haase is a player I know very well and he knows me very well, [he is a] dangerous opponent," he added.
"He hits the ball very hard so I need to be very focused on the serve because returning can be tough.
"[I need to] play solid and try to be ready to play a tough match."