Roger Federer and Juan Martin del Potro emulated Jo-Wilfried Tsonga's four hour set from Tuesday as they engaged in a prolonged match delaying the start of the other semifinal games that followed. In the end, Federer walked out as the victor advancing to the finals for the first time in his Olympic career. 

The match lasted over four hours and finished 3-6, 7-6, 20-18 in favor of Federer. 

Del Potro took the 17-16 lead and had the 40-15 advantage. Federer battled back winning points and eventually smacked an ace to stay alive, tying the set at 17.

By this point the match had hit the four hour mark. 

He took the 18-17 lead in the set and del Potro showed he was discourage while walking to his sit on side court. 

With a chance to wrap the match up with the 40-30 advantage, Federer hit a volley right into the net, setting up a tiebreaker for the match point. He captured the match point as del Potro hit a backhand into the net giving Federer the win. 

As people could tell from the score, del Potro was a worthy opponent.

Del Potro took the first set shocking the No. 1 ranked Federer.

Federer had one more ace than del Potro in that first set, but also committed a flurry of unforced errors that gave del Potro an edge.

By the end if the first set, Federer had seven unforced errors while the Argentinian only had two.

Del Potro took the first set 6-3.

Del Potro once again challenged Federer as the second set went into a tiebreaker. Federer won the set 7-6, allowing the Swiss tennis player to remain in the match avoiding elimination.

Federer will now wait for an opponent as Andy Murray and Novak Djokovic will face each other later on in the day.