Federer surprises kids testing rackets.

Roger Federer surprises a group of young tennis players who were testing rackets for Wilson and have no idea he is about to arrive.

1:14

Djokovic 'very grateful' for career.

Novak Djokovic talks about what he values most about being the favorite at the US Open.

2:07

Kerber is not talking about possible No. 1 ranking.

Angelique Kerber talks about the pressure she felt trying to win Cincinnati, and also take the No. 1 ranking away from Serena Williams.

0:39

Muguruza feels stronger and more experienced than ever.

Garbine Muguruza talks about her chances at the US Open and who may stand in her way.

0:48

Serena first felt shoulder pain after Wimbledon title.

Serena Williams talks about the shoulder injury that has been causing her problems since she won Wimbledon.

0:44

Nishikori: I've had a lot of special moments at the US Open.

Kei Nishikori reflects on some of his recent performances at the US Open.

0:33

Nishikori: Djokovic and Murray a level above.

Number six seed Kei Nishikori conceded that Novak Djokovic and Andy Murray are a level above everyone else ahead of the US Open.

0:29

Mauresmo backs Murray for glory.

Andy Murray's former coach Amelie Mauresmo has backed the Wimbledon champion for glory at this year's US Open.

1:21

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