Roger Federer has moved on to the London 2012 Olympic Semifinals in the Men's Singles event. He retired American John Isner in two sets 6-4, 7-6 in a very close match. 

Isner proved to be a worthy opponent as Federer struggled to build any kind of momentum against the American.

Isner started out by taking leads in the games he served in. With the game 4-4, however, Isner was not able to take the advantage and lost the fifth and sixth games of the first set.

A flurry of unforced errors forced Isner to lose the tiny momentum he had built. At times, it did not seem like you could really blame Isner for the errors. He is a lanky 27-year-old measuring 6'9" weighing in at 229 pounds.

He slipped while going back on a ball and at times looked like he would lose his balance.

Isner continued his assault on Federer in the second set. He had a little more control of his body this time.

The same pattern from the first set ensued in the second set.

Isner started serving and took a 1-0, 2-1. 3-2 , 4-3, 5-4 and 6-5 leads in the second set. He worked the net well in the final games he won.

Federer matched every one-game lead Isner took.

The fans were into this match after the 5-5 tie. USA cheers were drowned out by Swiss cheering for Federer.

Federer pushed it to a 6-6 tiebreaker and took the first point. Isner fought back to take the second point. Federer took the third point in the tiebreaker. Isner returned the favor. 

At this point the umpire had to remind the fans to remain calm. Isner served and won the fifth point holding the 3-2 advantage.  Federer then went back-to-back, taking the sixth and seventh points for the 4-3 advantage. 

Isner came back to win the eighth and ninth points for the 5-4 lead. Federer stayed in the match tying the game at five then aced his way to the 6-5 lead. He won the match on a floater that hit off the net and bounced on Isner's side of the court.