The 81-year-old was in charge of world football's governing body between 1998 and 2015, at which point he was forced to resign due to a corruption scandal and banned from all football activity for six years.
Speaking in an interview with Portuguese newspaper Expresso, former Seattle Reign keeper Solo claims that Blatter sexually harassed her before she went on stage to present an award at the glitzy ceremony four years ago.
"I had Sepp Blatter grab my ass," she said. "I was nervous for the presentation. It was the Ballon d'Or I was presenting. After that I didn't see him and that was kind of bad. I didn't get to tell him directly 'don't ever touch me'. That's the way I've always handled things - directly."
Disgraced former FIFA chief Blatter, via his spokesman, described the allegation as "ridiculous".