Mattson claimed she was "singled out for criticism for minor infractions because of her gender," according to the lawsuit, and that she was retaliated against "for standing up for her rights."
After the six-month suspension, Mattson was not assigned to events, nor notified of training opportunities, and was not allowed to have her certifications reinstated on the USTA website, her complaint said.
In her lawsuit, Mattson "reasonably estimates that she was denied access to 95 percent of the USTA events for the 2012-2013 season," and she was not assigned "for a single event until on or about August 15, 2013."
She claimed that "less qualified male individuals" were placed at the event she requested on Aug. 15.
Mitra Shahri, Mattson's attorney, said, "I read once that 'Sports don't build character, they reveal it.' That could not be more true with USTA. Our female tennis players have come so far because they were finally given a fair chance to compete, and this lawsuit is asking the same for our hard working female umpires."