The Saints had hoped that Hartley might return at some point this season, but they signed veteran John Kasay, who is 6 for 6 in field-goal attempts so far.
Hartley's agent, Erik Burkhardt, told The Times-Picayune in an e-mail Tuesday night that Hartley re-injured himself while trying to return from the original injury, though surgery will not be required.
"In an attempt to return quicker then he probably should have, Garrett suffered a setback when swinging his leg," Burkhardt wrote. "The original diagnosis was 7-10 weeks after the injury but the injury is somewhat rare so it's very hard to put a timetable on things. After the recent setback the team decided it would be best to make sure his treatment and rehab wouldn't be rushed so that he could get back to 100 percent by camp next season."