MASON: Novak Djokovic of Serbia returns a shot to Sam Querrey of the United States during Day 4 of the Western and Southern Open at Lindner Family Tennis Center in Mason, Ohio. - AFP

CINCINNATI: Worldnumber one Novak Djokovic got his US Open build up off to a smooth start with astraight-sets win in Cincinnati on Tuesday as back trouble forced SerenaWilliams to withdraw. Defending champion Djokovic double faulted three times ashe dropped serve in the opening game against Sam Querrey but quickly put thingsright and pulled away for a 7-5, 6-1 victory over the American.

"I ended thematch well even if the start was nervy," said Djokovic, who would breakQuerrey twice to take the first set then roll to victory in his first matchsince beating Roger Federer in the Wimbledon final last month. "Sam wasfeeling comfortable on the court at the start and dictating. It was toughfacing his big serve," Djokovic said. "I'm just pleased with thischallenge in quick conditions, I'm glad I overcame it. "I'm hoping for abetter performance in the next round."

Williams,meanwhile, was left just trying to get healthy before the August 26 start ofthe US Open, pulling out of her scheduled first-round match against qualifierZarina Diyas just days after she was forced to retire from the WTA Torontofinal with back spasms. "I came to Mason (Ohio) on Sunday and have triedeverything to be ready to play tonight, and was still hopeful after my practicethis morning," Williams said in a statement released by tournamentofficials. "But unfortunately my back is still not right."

It's anotherinjury blow for 23-time Grand Slam champion Williams, who was hampered by kneetrouble earlier this season and remains in search of her first title since the2017 Australian Open. In early action, Stan Wawrinka won a first-round battleas he eliminated 2017 Cincinnati champion Grigor Dimitrov 5-7, 6-4, 7-6 (7/4).Under leaden skies after an overnight thunderstorm, Dimitrov broke in the 12thgame of the first set to take the lead.

The 33-year-oldSwiss fought back with the only break in the second set. Wawrinka then racedinto a 5-1 lead in the final set but wasted two match points in the eighth gameand was broken twice while serving for victory. Wawrinka had to hold off hisBulgarian opponent in the final-set tiebreaker before squeezing through in morethan two and a half hours with his 10th ace. Wawrinka, who played a 2012 semi-finalhere, will face Russian qualifier Andrey Rublev, a 6-7 (4/7), 6-4, 6-2 winnerover 15th seed Nikoloz Basilashvili from Georgia. In other opening-roundmatches, Montreal semi-finalist Gael Monfils exited to Frances Tiafoe 7-6(9/7), 6-3 and Belgian David Goffin beat Taylor Fritz of the United States 6-4,4-6, 6-4.

VENUS TOPPLESBERTENS

In women's play,defending champion Kiki Bertens fell in the second round to Venus Williams,with the 39-year-old American putting her decades of experience to good use ina 6-3, 3-6, 7-6 (7/4) victory. "Before the match I felt quite good.Stepping on court, I'd say first few games was pretty bad," Bertenssaid.  "I didn't start the match ina loose way. I knew that I had to defend the title." Williams, who reachedthe semi-finals in 2012, has not been past the second round in Cincy sincethen.

Former US Openfinalist Madison Keys knocked out 2017 Cincinnati champion Garbine Muguruza ofSpain 6-7 (4/7), 7-6 (7/5), 6-4. Former number one Angelique Kerber continued adismal hardcourt summer, losing in the first round for a second straight weekas she fell 7-6 (9/7), 6-2 to Estonian Anett Kontaveit. - AFP