The defending champion is back in the final four at the ATP Finals, while preparation is underway for the final event on the ATP's calendar. Here are the Top 5 photos from Friday.

1

Finding himself in a must-win situation, Alexander Zverev saw off Daniil Medvedev, 6-4, 7-6 (4), to claim the final semifinal spot at the season finale in London. The German will meet Dominic Thiem Saturday evening for a chance to raise the trophy for the second year running.

2

Rafael Nadal battled past Stefanos Tsitsipas, 6-7 (4), 6-4, 7-5, to close out his ATP season with a victory. Despite going 2-1 this week, Nadal drew the short end of the stick in his group by losing more sets than Zverev and Tsitsipas.

3

Though he missed out on winning an elusive ATP Finals crown, all wasn't lost for Nadal. The Spaniard received the year-end ATP World No. 1 trophy for a fifth time, bringing him into a second place tie for the all-time lead alongside Roger Federer, Novak Djokovic and Jimmy Connors.

4

Andy Murray and his teammates trainted together in preparation for the new-look Davis Cup Finals. The competition, now held over one week in Madrid, begins Monday.

5

While Tsitsipas lost, he still finished on top in his group. As a result, the Greek will take on Roger Federer in the first semifinal on Saturday. The Swiss recently won an indoor hard-court encounter in Basel just a few weeks ago.