By Larry Fine
NEW YORK (Reuters) - Second seed Angelique Kerber stayed on track in her quest to unseat Serena Williams as world number one by beating Mirjana Lucic-Baroni of Croatia 6-2 7-6(7) on Wednesday to reach the third round of the U.S. Open.
Australian Open winner Kerber rifled home an ace to finish the first set against the free swinging, 34-year-old Lucic-Baroni, then won a see-saw second set in which each player was broken three times on the way to a tiebreaker.
The Croat held two set points during the decider before losing it 9-7.
The left-handed German was one match win away in Cincinnati from ending Williams' long reign as number one before losing to Czech Karolina Pliskova in the final and has another chance to leapfrog the American at Flushing Meadows.
Lucic-Baroni raised her game in the second set, but could not overcome the steady Kerber as the big-hitting Croat blasted 37 winners while gifting the German with 55 unforced errors.
(Editing by Mark Lamport-Stokes)