World number one Aryna Sabalenka suffered a major setback in her preparations for the US Open after losing to Russia’s Ekaterina Alexandrova in the fourth round of the Canadian Open in Toronto on Saturday. Alexandrova, the 16th seed, defeated the reigning US Open champion 7-6(3), 4-6, 6-4 in a fiercely contested match that lasted nearly two and a half hours. Alexandrova Holds Her Nerve in Deciding Set Sabalenka, a four-time Grand Slam champion, started strongly and broke early in the opening set. However,