A sweltering day at Montreal took its toll on the first round of the National Bank Open, as three players were forced to retire from their opening-round matches Monday. Eleventh-seeded Maria Sakkari of Greece advanced when the Czech Republic's Marie Bouzkova was forced to stop while trailing 6-4, 3-1. Another Czech player, qualifier Tereza Martincova, retired while behind 6-1, 4-3 to U.S. qualifier Amanda Anisimova. Aus