American Jack Sock said he shocked after moving from “thinking about his holidays” during his opening Paris Masters win, to qualifying for the World Tour Finals in London after claiming the Bercy title.

The 16th seed beat qualifier Filip Krajinovic 5-7, 6-4, 6-1 in the final on Sunday. He trailed 5-1 in a deciding set during his second-round match against Britain’s Kyle Edmund on Wednesday, but fought back before going on to snatch the eighth and final spot for the year-ending event from Spaniard Pablo Carreno Busta with the biggest title of his career.

Sock will rise from 22nd to ninth in the world rankings on Monday and is the first American to reach the Tour Finals since Mardy Fish in 2011. “Coming in this week I had no idea I could even make London,” the 25-year-old told a press conference.

“It wasn’t in my head. I just wanted to play some good tennis my last week and go start my off-season.

“Now to sit here and extend the season another two weeks, and to keep playing and achieve a lot of firsts today for me, is incredible.

“I was thinking about my holidays the next day (when a double-break down to Edmund). I tried to start shortening points and just going after my shots. They were landing and I was connecting a lot of them.”

Sock will also become the US number one for the first time in his career after winning his third ATP title of the season.

His victory was the first in a Masters tournament by an American since former world number one Andy Roddick took the Miami crown in 2010.

Sock said he would have nothing to lose when he arrives in London to take on the likes of Rafael Nadal and Roger Federer.

“I obviously snuck into the eighth spot in London unexpectedly, so zero pressure on me to go there,” he added.

“I’m going to swing big and play my game like I always do, and just, honestly, enjoy the moment.”