Stan Wawrinka has admitted that he is observing the techniques of top-players including Roger Federer's latest weapon known as 'Sneak Attack By Roger (SABR)', which is the reason for his improvement in the last few years.
SABR is a new chip-and-charge approach on second serve which has been developed by the Swiss great.
The 30-year-old also lauded Federer, saying that the way latter has been playing right now is quite impressive, Sport24 reported.
Earlier, Wawrinka claimed 6-4, 6-4, 6-0 quarter-final win over South Africa's Kevin Anderson in the ongoing US Open.
The French Open champion will next face World number two Roger Federer, who also advanced to the semifinals by overcoming Richard Gasquet 6-3, 6-3, 6-1.