For the fifth year in succession Roger Federer and Novak Djokovic will meet at the US Open and if the former can maintain his level of form so far in the tournament, he has the capability of dumping out the world number one.
Federer was especially impressive when defeating Jo Wilfried Tsonga in straight sets in his quarter final and admitted himself that he was pleased with the performance.
It was his movement around the baseline and ability to hit forehand winners from all angles that caught the eye and a repeat of this could give Djokovic problems.
Federer has won three of his previous four US Open meetings with Djokovic and also inflicted a rare 2011 defeat on the Serbian in the semi finals of the French Open back in June.
The US Open tennis odds have Federer priced at 6/4 to beat Djokovic and this may prove to be a big price, particularly as Djokovic was perhaps marginally lucky to win his quarter final.
Djokovic was involved in a tense battle with compatriot Janko Tipsarevic in the last round, but eventually pulled through in three hours, although his opponent was troubled by a leg injury that caused his retirement.
With Djokovic only having lost two matches all season, he is especially tough to beat and therefore 8/15 could be great value that he beats Federer.
Meanwhile, Djokovic has already beaten Federer in the semi finals of a hard-court Grand Slam this year, back in January on his way to winning the Australian Open.
Djokovic is undoubtedly the more consistent player now he has reached the peak of his powers and his formidable defence may be the defining factor of a tight semi final.
In the set betting market, Djokovic winning in four sets looks the pick at 11/4, but if Federer can find an early rhythm and then maintain it, 9/2 looks reasonable that he triumphs 3-1.