Injury-cursed Tommy Haas, a former world number two, made his latest return to action on Tuesday after a 14-month absence at the Munich claycourt tournament.
The 33-year-old teamed up with the Czech Republic's Radek Stepanek, losing in the doubles to Simon Aspelin and Paul Hanley.
Haas last played on the tour in February 2010 before undergoing surgery on his shoulder and right hip.
"I always have the ambition. It'll take time to reach the stage where I hope to be, perhaps I'll no longer reach the level that I once had. But I think I can play another two seasons on the tour," said Haas, a 12-time title winner.
Haas, who no longer has a singles world ranking, hopes to play the Madrid and Rome Masters as well as the French Open but will need wild cards in order to do so.