What happened to Eugenie Bouchard in loss to qualifier?

In an absolute stunner, Eugenie Bouchard was ousted from the Rogers Cup in Montreal on Tuesday to American qualifier Shelby Rogers. So how could this happen?

Source: http://www.cbc.ca/sports/tennis/what-happened-to-eugenie-bouchard-in-loss-to-qualifier-1.2728643?cmp=rss