U.S. No. 1 Isner doubt for Australian Open
The United States' top male tennis player John Isner is in danger of missing the forthcoming Australian Open with a knee injury.
Top seed Isner crashed out in the second round of the Sydney International warm-up event to fellow American Ryan Harrison on Wednesday and complained of a recurrence of the injury which kept him out the recent Hopman Cup tournament.
"I could play, but from now up until Melbourne I definitely can't practise like I need to," the world No. 13 told the ATP Tour's official website.
"Certainly I could win a match maybe, a match or two. I don't see myself winning the whole tournament at this point, that's for sure."
Isner, a winner of five titles since turning pro in 2007, has never advanced beyond the fourth round of the year's first grand slam.
The 27-year-old's best performance in one of tennis' four marquee tournaments came in 2010 when he reached the quarterfinals of the U.S. Open.
Harrison chalked up his first ever win over an opponent ranked inside the world's top 15 with a 6-4 6-4 success.
"(I) had to save a couple break points early, but then once I got past those I felt like I served really well and was able to start cashing in a lot rhythm from the ground," said the 20-year-old, who will play Frenchman Julien Benneteau in the last eight.
"If you take a good crack at a return, even if you miss it by a little bit, at least he feels it. That can cause some double faults."
Australia's Bernard Tomic is the only player inside the top 100 younger than world No. 68 Harrison. Tomic, ranked 64th, delighted the home crowd by defeating fifth seed Florian Mayer 7-6 (7-4) 6-2.
"There is talk now that I'm serving really good and my groundstrokes are really good, too," explained the 20-year-old. "I'm moving really well. There is nothing much more I can ask myself at this stage.
"I think I'm getting much more angle in the court, it's not about how hard you hit the serve. I love serving like that. Even if they get it back, you've got the whole court to do anything you want with the shot."
Tomic's reward for his win is a meeting with defending champion Jarkko Nieminen, who beat Slovakian lucky loser Ivo Klec.
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