By Larry Fine
NEW YORK (Reuters) - Twice Australian Open champion Victoria Azarenka overcame an inspired challenge from qualifier Aleksandra Krunic of Serbia 4-6 6-4 6-4 on Monday to advance to the quarter-finals of the U.S. Open.
Azarenka, who began the year as world number two and slipped to a 16th seed after dealing with foot and knee injuries, took a 3-0 lead in the first set before the 21-year-old Serb, ranked 145th, roared back and claimed the set.
Krunic, on course to graduate college with an economics degree this year, continued to press the Belarussian, coaxing 40 unforced errors in the two-hour 19-minute match but in the end Azarenka's power and experience proved the difference.
It ended an enthralling run by the diminutive Serb, who won three qualifying matches, beat 27th-seeded American Madison Keys in the second round and third-seeded Wimbledon champion Petra Kvitova of the Czech Republic in the third round.
Azarenka, the U.S. Open runner-up to Serena Williams the last two years who withdrew from seven tournaments this year due to injuries, will play Russian 17th seed Ekaterina Makarova, a 7-6 6-4 winner over a heat-stricken Eugenie Bouchard of Canada.
"Aleksandra played some amazing tennis. She has a great future," Azarenka told the Arthur Ashe Stadium crowd. "I think it's never easy to play someone you don't know. I just tried to stay positive and fight."
(Reporting by Larry Fine; Editing by Nick Mulvenney)