The 38-year-old Briton, who has previously been a world number one but has never won any of the four major championships, said his putting had "let me down" at the US Masters earlier this month.
Westwood finished tied third at Augusta but hopes he can again take the number one spot in the $750,000 Indonesian Asian Tour event at the Royale Jakarta Golf Club, which tees off Thursday.
Speaking of his US performance, Westwood said: "I played well to the greens, probably well enough to win the tournament, but if you don't putt well, then you're not going to win any tournaments."
He refused to respond to questions as to whether he would fire his putting coach Phil Kenyon. Chubby Chandler, the head of his management company, has criticised Kenyon for Westwood's performance in Augusta.
Westwood said he aimed to return to the number one rank, a position he occupied briefly after winning the Indonesian event last year.
"I'm not far off at the moment in third place," he said, adding that he was looking forward to the Indonesia event.
"It is always special to come back here. It is nice to come back and try to defend but I don't think it will be easy. It is tough to win one and it is even tougher to defend.
"I mastered the course last year and had the game plan right. All the players playing here wouldn't be in this tournament if they weren't capable of winning. No matter where you play in the world now it is difficult to win."