Tomas Berdych has admitted that he was not clinical enough after losing to Stanislas Wawrinka at the ATP World Tour Finals in London.
The Czech world number six was beaten 3-6 7-6(0) 3-6 by Wawrinka in the opening match of the tournament on Monday.
"Losing is not a good start but there are still two other matches to go," BBC Sport quotes Berdych as saying. "It was really about the small chances - Stan was better in executing the chances.
"He had four break points and made two; I had five, made zero. I think that's been a really big difference today."
World number one Rafael Nadal and David Ferrer join Berdych and Wawrinka in Group A of the season-ending event.
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