So much for the first US Open match-up between Roger Federer and Rafael Nadal.

Federer failed to live up to his end of the bargain.

Hours after Nadal did his part with an easy-as-can-be victory to get to the semi-finals at Flushing Meadows, Federer was unable to join him for what would have been the most-anticipated showdown of the entire two weeks, wasting chances to take control and missing shots he normally makes in a 7-5 3-6 7-6 (8) 6-4 loss to 2009 champion Juan Martin del Potro on Wednesday night.