Djokovic beats Pouille to reach Cincinnati semi-finals

Novak Djokovic wore down Lucas Pouille after an even first set, dispatching the Frenchman 7-6(2), 6-1 in a Cincinnati Masters quarter-final in Ohio on Friday.

The match was much closer than when the pair met in the Australian Open semi-finals in January, when Djokovic conceded only four games before going on to win the title.

It took Djokovic nearly an hour to prevail in the first set but he closed out a one-sided tiebreak with a deft backhand passing shot.

The second was one-way traffic as the world number one played with relentless efficiency against an opponent who ran out of answers.

Perhaps the only concern for Djokovic with the US Open looming in less than two weeks was a sore elbow which required brief treatment by his trainer late in the match.

"I managed to finish the match, had a little bit of tightness in my elbow but hopefully everything will be fine for tomorrow," Djokovic said in an on-court interview.

He will have less than 24 hours to recover for a semi-final against Daniil Medvedev, who continued his recent hot form, ousting Russian compatriot Andrey Rublev 6-2, 6-3 in barely an hour.

Medvedev, a career-high eighth in the rankings, faced only one break point.

He has made two finals in the past two weeks, losing to Nick Kyrgios in Washington and Rafa Nadal in Montreal.

In other quarter-final action, Frenchman Richard Gasquet continued his comeback from groin surgery by defeating 11th seeded Spaniard Roberto Bautista Agut 7-6(2), 3-6, 6-2.

Gasquet, who defeated Andy Murray in the opening round, set up a semi-final clash on Saturday with Belgian 16th seed David Goffin.

Goffin advanced when his quarter-final opponent, Japan's Yoshihito Nishioka, pulled out before their match on Friday due to illness.

Gasquet underwent groin surgery in January and returned to competition in May.

"I didn’t play for six months, so it's great to be back here and reaching the semi-finals aged 33," Gasquet told ESPN in an on-court interview.

"Goffin is a tough guy, one of the fastest from the baseline, so I will be prepared to battle and to fight."

Knee injury puts Osaka's US Open title defence in doubt

World number one Naomi Osaka will "probably" defend her US Open title, even if it means defying her doctor's orders, she said after retiring from the Cincinnati Masters with a knee injury on Friday.

Osaka was trailing American Sofia Kenin in the third set of their quarter-final in Cincinnati when she sought treatment on her heavily-strapped left knee.

After briefly returning to play, the Japanese star retired with Kenin leading 6-4, 1-6, 2-0.

Osaka's withdrawal comes after Serena Williams, the woman she beat in a tumultuous final at Flushing Meadows last year, pulled out of Cincinnati with back problems.

The injury has also loosened Osaka's grip on the top ranking, with world number two Ash Barty poised to reclaim it if the Australian makes the final.

"I really don't know what's going on with my leg right now," Osaka told reporters.

"It sucks, especially since I didn't want to get injured this close to the Open, and now I'm kind of worried a little bit.

"The thing is, my pain tolerance is really high, so that's usually why I play through things that apparently I shouldn't."

Osaka said she "felt it wasn't safe" to continue against Kenin ahead of the U.S. Open starting Monday week.

"I feel like this might have that one percent chance of me not being able to play, and that's what's concerning me.

"In the end, I'm going to play even if the doctor says no, probably."

Osaka's retirement sent Kenin through to face fellow American Madison Keys in Saturday's semi-final.

Keys faced only two break points in beating Venus Williams 6-2, 6-3 in the evening encounter.

Barty will face Russian veteran Svetlana Kuznetsova in the other semi-final after rallying to a 5-7, 6-2, 6-0 victory over Greek Maria Sakkari.

The Australian had surged to a 4-1 lead in the first set before she stumbled with unforced errors, with Sakkari lifting to take control through a slew of backhand winners.

Barty cleaned up her game in the second set, however, recovering the backhand slice that had deserted her in the opener.

"It was important for me at the start of the second set to go back to basics and what worked before," the 23-year-old Barty said.

"I had to serve well, and not give her too many looks at second serves. I tried to bring in my slice to change the tempo of the match."

Kuznetsova outlasted Czech third seed Karolina Pliskova 3-6, 7-6(2), 6-3, having been a set down with her opponent serving for the match.