Roger Federer was a break up in the first set against Taylor Fitz when rain set in for the evening, ending his comeback after seven games at the Mercedes Cup on Wednesday.
The break put top-seeded Federer 4-3 up against the American teenager, whose big serve deserted him in that seventh game. But steady rain then forced organizers to abandon play for the day.
Federer is returning from a back injury that forced him to miss the French Open. The Stuttgart event is a tune-up for Wimbledon, where Federer is a seven-time champion.
Federer’s second-round match will resume Thursday, with the winner to play qualifier Florian Mayer, who beat Michael Berrer 6-3, 3-6, 6-4.
Seventh-seeded Philipp Kohlschreiber beat Denis Kudla 7-5, 6-3 to reach the quarterfinals.