"I suffer from groin problems since Wimbledon," said the 24-year-old Italian, who lost in the first round of the Swiss Open last week. "My problems got worse there. I am sorry, it simply won't work."
Seppi, ranked 34th, was to headline the tournament after the top three seeded players -- Paul-Henri Mathieu, defending champion Juan Monaco and Juan Carlos Ferrero -- all withdrew with injuries last week.
Seppi was replaced in the draw by Matthias Bachinger of Germany, who lost to Devilder 6-3, 6-3.
Devilder next plays Alexander Peya of Austria, who lost the opening set to 2003 champion Guillermo Coria 7-5 but advanced when the Argentine retired with a right shoulder injury before the start of the second set.
Juan Martin del Potro beat Josselin Ouanna of France 6-3, 6-3. The seventh-seeded Argentine, who won last week's Mercedes Cup for his first ATP title, was in control of the match throughout.
The 26-year-old Romanian, who won his first ATP event at the Swiss Open last Sunday, trailed 2-0 in the tiebreaker before winning seven straight points to close out the match.
No. 8 Olivier Rochus was eliminated after Ivo Minar of the Czech Republic rallied to beat the Belgian 3-6, 6-4, 6-0. No. 4 Potito Starace, No. 5 Eduardo Schwank and No. 6 Jurgen Melzer all had straight-set victories.