Novak Djokovic, the second seed from Serbia, advanced to the semifinals of the season-ending ATP World Tour Finals with a three-set defeat of Juan Martin del Potro of Argentina.
Djokovic won 6-3, 3-6, 6-3. Having beaten six-time champion Roger Federer in the first round of the tournament at the O2 Arena in London, Djokovic joined top-ranked Rafael Nadal in the semifinals with his win. Federer, who defeated France’s Richard Gasquet 6-4, 6-3 in an afternoon match, will play del Potro in two days for the other semifinal spot from group B.
The tournament brings together the top eight men for a season finale. Djokovic is the defending champion, while Nadal’s best finish is a loss to Federer in the 2010 final.