Jack Sock's unlikely challenge for a place at the ATP Finals continued on Saturday as the American defeated Julien Benneteau in straight sets to reach the Paris Masters decider.

Sock, ranked 22nd in the world and seeded a distant 16th for the ATP 1000 event in the French capital, must win what would be the biggest title of his career if he is to reach the season-ending event at London's O2 Arena, an unexpected berth that would come at the expense of Pablo Carreno Busta.

Frenchman Benneteau was a popular winner against Marin Cilic in the quarter-finals but he was unable to deliver in the last four at the Bercy Arena, where Sock won 7-5 6-2 in one hour and 19 minutes. 

He will face Filip Krajinovic in the decider after the Serbian qualifier stunned John Isner earlier in the day to end the American number two's Finals hopes.

Breaks were traded freely in an inconsistent opening set, but it was home favourite Benneteau who fell behind at the crucial moment, giving up his serve in the 11th game and seeing Sock hold to take the opener. 

He saved a break point in the fifth game of the second set but a double fault then gifted the American the advantage.

From there the Frenchman fell apart, as another double fault in his next service game saw Benneteau present Sock with three break points.

The world number 83 saved two of them but threw in yet another double fault to offer his opponent a chance to serve for the match, which Sock had no hesitation in capitalising on.