 Later in his career , Federer added the drop shot to his arsenal and can perform a well @-@ disguised one off both wings . He sometimes uses a between @-@ the @-@ legs shot , which is colloquially referred to as a " <unk> " or " <unk> " . His most notable use of the <unk> was in the semifinals of the 2009 US Open against Novak Djokovic , bringing him triple match point . Federer is one of the top players who employs successfully the " <unk> shot " , when he gets pushed deep and wide on his forehand wing . Since Stefan Edberg joined his coaching team at the start of the 2014 season , Federer has played a more offensive game , attacking the net more often , and improved his volley shots . In the lead @-@ up to the 2015 US Open , Federer successfully added a new unique shot to his arsenal called <unk> ( <unk> Attack by Roger ) , in which he charges his opponent while receiving the serve and hits a return on the run . 
