Llodra win over Soderling is Frenchman's second title in 2008
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The 27-year-old Llodra, who also won the Ordina Open in 2004, dropped his first set of the week but the world's 58th-ranked player fought back to break Soderling twice in the second.
Both players dominated on their own service in the final set but Llodra's serve and volley game earned him victory in the tiebreak.
"I came here this week and saw the draw and knew it would be difficult and so it is unbelievable I'm standing here with the trophy," said Llodra, who is the third French winner of the tournament following Cedric Pioline and Nicolas Escude (twice).
For Llodra the victory in Rotterdam, after winning in Adelaide in January, was further proof that the doubles specialist's decision last year to develop his singles game was paying off.
"This win gives confidence ... at the end of February I won two titles already," said Llodra.
"Also today, after losing the first set and surviving two break points in the opening game of the second one, I have the feeling I played one of my best matches on the tour.
"I knew that Robin might get a bit nervous when you put him under pressure and therefore I changed my game a bit during the match and pressurized his second serve and that finally gave me the win."
Soderling, ranked 59th in the world, was happy with his performance in only his second tournament since he came back from a left wrist injury that had sidelined him for months. He reached the quarterfinals in Marseille last week.
"[Llodra] really played well on the important points and therefore deserves the victory," Soderling told reporters.
"It was different today as we only had three or four rallies while my previous four matches were all against baseliners. I played some poor service games in the second set but overall I am pretty much on the level I want to be."
Reuters and The Associated Press contributed to this report.