Croatian Ivan Ljubicic defeated Andy Murray 6-4, 6-4 on Saturday to lift the trophy at the $1 million Qatar Open.
World number five Ljubicic, who won three titles in 2006, relied on his big serve and fluent backhands to wear out the British number one in the final.
"It's a great feeling to come back and win here after being runner-up in 2004 and 2005," the 27-year-old Croat told reporters.
"The crowd has been fantastic and it's a great feeling to be number one in the ATP Champions Race...although it may be for a short period."
The ATP Champions Race is a calendar-year points system while the world rankings are always based on the previous 52 weeks of tennis action.
Murray, who joined Spaniard Rafael Nadal as the only players to beat world number one Roger Federer in 2006, fought well but lacked experience on the big points.
SLICED BACKHANDS
The 19-year-old Scot troubled his opponent with his double-handed backhand and top-spin forehand but Ljubicic, relying heavily on his booming serves and sliced backhands, wriggled out of several tight spots.
Ljubicic, leading 5-4, broke serve in the 10th game to clinch the first set.
In the second, Murray broke Ljubicic in the fifth game to go 3-2 up.
The Scot was 0-40 down in the sixth game and, though he saved two break points, Ljubicic broke back to make it 3-3.
Ljubicic then broke again in the 10th game to wrap up the match.
"Murray is a tough opponent. I had to be aggressive but not too aggressive," Ljubicic said.
"I had to have a mix of baseline and net play. I just waited for the points because he doesn't make too many mistakes."
Murray was playing in the fourth final of his career. He has one title to his credit at San Jose last year.
"Ivan is a great player and a great fighter and I lost to a better player today," Murray said.
"It was freezing cold out here throughout the week but we played some really good tennis. I am happy with the way I played for the most part and I look forward to continuing the good form in Australia."
The season's first major, the Australian Open, takes place in Melbourne later this month.
