Jordan Spieth says he did not envisage having the chance to become world number one this season.

The Masters and US Open champion would overhaul Rory McIlroy at the top of the official world golf rankings if he can claim a first World Golf Championship victory in the Bridgestone Invitational at Firestone CC this week.

Spieth says his intention this year was to climb the rankings, but he did not expect to progress so quickly.

“At the beginning of the year, I wanted to work my way up the world ranking. I didn’t think I could be in this position or have this opportunity,” Spieth said. “I feel blessed with how this year’s gone.”

Spieth will have to improve dramatically on his Firestone debut 12 months ago where he finished 49th in the 72-man field and failed to break par in any of the four rounds in the non-cut event.

The 22-year-old admits he struggled to cope last year and he feels a good week with the driver is the best way to improve his chances of success. He also believes it will be ideal preparation for the season’s final major at Whistling Straits in Wisconsin next week.

“It’s a big, meaty golf course,” Spieth said. “It’s a tough one. I struggled with it last year. It’s going to take some really strong driving of the golf ball to put ourselves in good enough position to hold these greens. From there it’s not over. Tee to green, I think it’s a really good prep for next week, and the greens putt similar.”

Spieth is 11/2 to win the Bridgestone Invitational while Jason Day is 12/1 and Rickie Fowler is 16/1.