Novak Djokovic is playing for a lot more than just a record-tying sixth title at the ATP finals.
The second-ranked Serb is also looking to reclaim the No. 1 ranking.
Djokovic won his third straight match at the season-ending tournament on Thursday, beating David Goffin 6-1, 6-2 at the O2 Arena to finish group play undefeated for the fourth time in the past five years.
But there are some more matches to play before the 12-time Grand Slam champion can be assured of finishing another season as the top-ranked player.
"Everything has been going ... in a positive direction. I've been playing better and better as I proceed in the tournament," Djokovic...