Andy Murray was content with his performance after beating David Ferrer in straight sets in his first match of the ATP World Tour Finals on Monday.
World number two Murray triumphed 6-4 6-4 against the Spaniard in the Ilie Nastase Group opener at the O2 Arena.
Eight double faults - one of which gifted the first set to Murray - cost Ferrer as he suffered a fifth successive defeat against the Scot.
Murray is attempting to reach the final of the season-ending tournament for the first time before playing in the Davis Cup final for Great Britain against Belgium next week.
The two-time grand slam champion said there was room for improvement following his straight-sets win, but felt Ferrer's style of play helped him get into his stride.
"The first couple of games my timing was a little bit off. But I got it back pretty quickly, which was pleasing." he said.
"You know, if you're looking for a little bit of rhythm, he's also a guy who makes you hit a lot of balls. The rallies are often quite long, so you can get into a rhythm against him. So that was good.
"Returns were a little bit off today, especially on the second serve. He obviously served a bunch of double-faults, which helped. But I could have returned a bit better.
"And that was the one thing, that obviously the ball's coming through a little bit quicker and slightly lower than on the clay. That was the one thing I think I could have done better today."