Serena Williams is on fire! After beating Danka Kovinic 6-3 in her first match at the US Open on Monday, the tennis professional beat Anett Kontaveit after three sets. The first set was close for Williams, who only beat her by one point, 7-6. But Kovinic came back ready for vengeance, winning the set 6-2.Williams put the second set behind her, and came back hard for the third, resetting and taking the final round 6-2.