Former US Open champion beaten in straight sets 6-1, 6-3 by Delbonis at Argentina Open
Former US Open champion says his knee troubles have him ‘living a nightmare’
Injury-prone former US Open champion handed wild card to compete at next week’s ATP Argentina Open
2011 and 2015 champion, will be looking to complete the Wimbledon-US Open double for a third time
Argentine will now face Rafael Nadal is US Open last-four encounter
Former world number one beat Argentina's Juan Martin del Potro 6-3 6-4 win on Monday