Recovering from knee surgery, Tsonga outlasts Dlouhy in Thailand
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Still lacking fitness after undergoing knee surgery three months ago, Tsonga looked jaded throughout the two-hour match but sealed victory with a 7-1 win in a final-set tiebreak.
"It was a very difficult match, I didn't play my best tennis," Tsonga said. "I won, that's the main thing, because Lukas was playing some good tennis. It's a good victory for me because I haven't played so much.
"I served well, I was there, I fought, and I won."
Since he reached the final of the Australian Open in January, Tsonga's season has been blighted by injury, causing him to miss the French Open and Wimbledon. He has played only last month's U.S. Open since his knee operation.
The lanky Monfils injured his leg after falling over several times during the match but was pinning his hopes on a speedy recovery.
"I don't feel so good now but we'll see tomorrow," he said. "I played solid and consistent. I broke him early in the match and played OK after that."
In first-round matches, Serbia's Marko Djokovic, younger brother of top-seeded Novak, suffered a drubbing on his ATP main draw debut. He was beaten 6-2, 6-0 by fifth-seeded Jarkko Nieminen.
Italy's Simone Bolelli dispatched with Thomaz Bellucci of Brazil 6-3, 6-3; Mischa Zverev beat Australia's Robert Smeets 6-4, 6-4; and Serbia's Viktor Troicki advanced after beating France's Fabrice Santoro 7-6, 6-2.