MASON, Ohio -- Venus Williams left her winning touch in Canada.
Williams knocked off sister Serena while reaching the finals in Montreal on Sunday, finishing runner-up. She lost to Lucie Safarova 6-7 (2), 6-3, 6-4 in the first round Tuesday.
"I wish I could have felt today like I did in Montreal, just to make it more competitive," Williams said.
The tournament lost its other defending champion when Victoria Azarenka withdrew because of an injured right knee.
Williams had an energizing week in Canada and hoped to keep their momentum going in Cincinnati, using it as a springboard to the U.S. Open. But her successful week came with a cost.
Williams arrived Sunday night and opened Tuesday morning, leaving little time to recover from her deep tournament run.
"Yeah, it was definitely a quick turnaround," she said. "Maybe it would have been a little better to play a little later in the day. But I think she just played so well. No matter what shot I hit, she hit a winner."
Safarova led 5-2 in the third set and appeared to have won a match point, but Williams challenged and the call was overturned. Williams rallied to win the set and then another.
"That's a terrible feeling," Safarova said. "You think you've won and you have those emotions, and suddenly, you're back in the match against a great player. Then she broke me, and I thought, 'Uh, oh.' I've lost matches on challenges before. I told myself, 'I'm not losing this one."'
Azarenka's withdrawal is the latest setback in a season full of injuries. She's been sidelined for much of the year with an ailing left foot. She aggravated an injury to her right knee at Montreal, where she lost in the quarter-finals, and hoped a few days of rest would take care of it.
She decided to withdraw after practising Tuesday morning.
"I started to feel a little bit better and did everything I could, but it's just not enough time for me to feel good to play a full match," she said. "I'm going to get more treatment and get more work done and should be good for the U.S. Open."
Fifth-seeded Maria Sharapova broke Madison Keys to go up 3-0 in the final set and held on for a 6-1, 3-6, 6-3 win that was gratifying. She was coming off a loss in the third round at Montreal.
"I didn't have a great week last week," she said. "No matter who is across the net, it's never easy going out in the first round because you want to change that result around. You want to change your attitude and your performance and obviously the result."
Freelance writer Mark Schmetzer contributed to this report.