Tsonga, the Australian Open runner-up, missed a month because of the right knee injury and lost in the first round of the Rome Masters last week to Gilles Simon. Tsonga is seeded 14th at the Hamburg event, a major clay-court warmup for the French Open.
Also Monday, 10th-seeded Mikhail Youzhny lost to Fernando Verdasco 6-3, 6-2 and 12th-seeded Juan Monaco advanced when Filippo Volandri pulled out with a knee injury with Monaco leading 6-1, 4-0.
Top-ranked Roger Federer and No. 2 Rafael Nadal had time to practice Monday - the top eight seeded players have first-round byes.
Both are coming off losses at the Rome Masters. Nadal lost for only the second time in his last 105 matches on clay, falling to Juan Carlos Ferrero 7-5, 6-1 in the second round. Federer lost to Radek Stepanek 7-6 (4), 7-6 (7) in the quarterfinals. With both of them out, the Rome title went to third-ranked Novak Djokovic.
Nadal at least had the excuse of an open blister on his foot.
"It's much better. Not perfect, but for sure better,'' Nadal said Monday.
Nadal has complained that the European clay-court season has been crammed together this year without a week off between any of the tournaments.
"After Rome, I had to come here,'' said Nadal, conceding that he might have skipped Hamburg if he had lasted until the final in Rome.
"Four straight weeks on clay, that is too much,'' said Nadal, who won the tournaments in Monte Carlo and Barcelona before going to Rome.
Nadal may be the dominant player on clay, but Federer rules in Hamburg. Nadal has played in Hamburg only twice before, and lost last year's final to Federer, who ended Nadal's 81-match winning streak on clay.
Federer has won the Hamburg event four times. His first victory came in 2002, when he broke into the top 10.
"I've done particularly well here and I always play unbelievable tennis in Germany,'' Federer said.
Federer has had a troubled season so far, after having mononucleosis at the start of the year. His only title came at a relatively small clay-court event in Estoril last month.
The loss in Rome was his sixth of the year, but Federer said he wasn't feeling more vulnerable.
"It's a distorted picture, because this year I am focusing more on the Masters Series and the Grand Slams and I am not playing so many events,'' Federer said. "I feel I am moving well, playing my normal tennis again.
"I was unhappy with the way I played in Rome, but it happens sometimes. I have to make sure it doesn't happen too often,'' Federer added. "The more you lose, the more they believe they can beat me. But believing is not enough, you still have to beat me.''
Federer said he would start worrying if he didn't do well at the year's remaining Grand Slams - the French Open, which he has never won, Wimbledon and the U.S. Open.
"Then, it would be a different situation,'' said Federer, who needs two Grand Slam titles to pull even with Pete Sampras at 14.
No way! Nadal suffers rare loss on clay court
