Novak Djokovic coach &lt;a gi-track='captionPersonalityLinkClicked' href=/galleries/search?phrase=Boris+Becker&amp;family=editorial&amp;specificpeople=67204 ng-click='$event.stopPropagation()'&gt;Boris Becker&lt;/a&gt; (C), &lt;a gi-track='captionPersonalityLinkClicked' href=/galleries/search?phrase=Alec+Stewart&amp;family=editorial&amp;specificpeople=213485 ng-click='$event.stopPropagation()'&gt;Alec Stewart&lt;/a&gt; (L) and Marian Vajda (R) watch on during the match between Novak Djokovic of Serbia and Roger Federer of Switzerland during day three of the Barclays ATP World Tour Finals at the O2 Arena on November 17, 2015 in London, England.