Lee Westwood ended the first round of the Indonesian Masters two shots off the lead after carding a 68.
If Westwood wins the tournament he could leapfrog Martin Kaymer, who is playing this week, and return to the world number one spot.
However, even if Westwood triumphs, fellow Briton Luke Donald could overtake him and Kaymer by winning The Heritage in the United States.
Donald shot a first round 67 as he made a promising start in South Carolina.
The 33-year-old carded five birdies and a bogey on his way to four under at Hilton Head Island.
The Heritage carries more ranking points than the Indonesian Masters but Westwood, who became world number one for the first time in October 2010 before being toppled by Kaymer, was remaining philosophical on the rankings battle.
"I'll let things take their course and see what happens at the end of the week. Like I said before, I'm here to win a golf tournament," said the world number two.
Westwood birdied his final two holes to move to within two shots of leader Siddikur of Bangladesh.
"I played solidly but I was a bit frustrated out there," added Westwood, who will be 38 on Sunday.
"It has been the story for me so far, hitting it great from tee to green and giving myself a lot of chances but not taking it."