As soon as it looked like Novak Djokovic was headed for his offseason vacation, the top-ranked Serb started playing his best tennis.
Djokovic was broken late in the first set and again early in the second, but he then found his stroke and quickly rebounded to beat Juan Martin del Potro 4-6, 6-3, 6-2 Sunday and reach the championship match at the ATP finals.
''He was set and a break up. He was the better player on the court throughout the first part of the match,'' Djokovic said. ''I managed to turn it around and played better.''
Djokovic will face either six-time champion Roger Federer or Andy Murray in Monday's final. Federer and Murray were to play later Sunday in the other semifinal match.
Del Potro took the lead late in the first set, breaking Djokovic for a 5-4 lead before serving out the set at love.
The tall Argentine, who defeated Djokovic to win the Olympic bronze medal at Wimbledon this year, then went up a break early in the second set. But Djokovic broke right back ...