Donald would have jumped from No. 3 to No. 1 with a victory, but lost to Brandt Snedeker on the second hole of a playoff in The Heritage at Hilton Head Island.
Donald saved par from difficult spots on the 71st and 72nd holes
to force the playoff, then did it again on the second extra hole.
But his luck ran out on Harbour Town Golf Links' closing lighthouse
hole, No. 18, when he got a partially buried lie in a front bunker.
"It was going to be some big rewards if I won today," Donald
said. "But I'll try and find the positives from this week and move
After waiting out a lightning delay on the final hole, Westwood finished off a 3-under 69 for a three-stroke victory over Thailand's Thongchai Jaidee.
The English star, ranked second behind Martin Kaymer entering the week, won on his 38th birthday.
Asked what he wanted for his birthday, Westwood replied, "Something silver and shiny."
As he stepped off the 18th green a portion of the gallery sang "Happy Birthday."
Westwood finished at 19-under 269 in the Asian Tour event at Royale Jakarta. He took a five-stroke lead into the final day after opening with rounds of 68, 66 and 66.
"It was quite a day, really," Westwood said. "I knew it wasn't going to be easy with a five-shot lead. I'm experienced enough to know that patience is the key.
"I hit the ball great, but didn't hit the putts when it mattered."
He did hole a tricky birdie putt on No. 11.
"It was probably the hardest putt I had all day. it was 15 feet with 3 feet of break," he said.
Jaidee shot a 65.
Information from The Associated Press was used in this report.