MELBOURNE, Australia (AP) -- The injuries are mounting at the Australian Open, though for the most part, players are coping with the oppressive heat.
No. 13-seeded John Isner and No. 21 Philipp Kohlschreiber were among five players who dropped out of the tournament on Tuesday, joining No. 12 seed Tommy Haas and two other players who withdrew on Monday.
Despite temperatures reaching 42 Celsius (108 Fahrenheit) during the afternoon and a hot breeze gusting over Melbourne Park for most of the day, none of the withdrawals were apparently linked to the oppressive heat.
Isner retired from his match against Slovakia's Martin Klizan with a lingering ankle injury that he said got progressively worse at the Hopman Cup event in Perth and a tournament he won in Auckland, New Zealand, over the past two weeks.
''I know movement is not the best part of my game,'' the 2.08-meter (6-foot-10) American said, ''but at a certain point I've got to be able to move without pain and I wasn't able to do that today.''
He withdrew before last year's Australian Open with an injury, as well.
''I thought I had a good shot at playing this match and winning this match and I pulled out,'' he said. ''I could have done the same last year, but I went home.''
The other seeded player in his section of the draw, Philipp Kohlschreiber of Germany, withdrew before his scheduled first-round match against Slovenian Aljaz Bedene.
He was replaced in the draw by Frenchman Stephane Robert, a lucky loser from qualifying, who defeated Bedene to reach the second round.
Czech veteran Radek Stepanek later retired from his match against Slovenian Blaz Kavcic with a neck injury while leading 7-6 (3), 6-4, 1-6, 0-2 after nearly three hours of play.
He said the problem started in the first set and got progressively worst throughout the match.
German Julian Reister also quit while trailing Brazilian qualifier Thomaz Bellucci 4-6, 6-3, 7-6 (5). A reason for his withdrawal was not immediately given by tournament officials.
A few other players struggled in the heat on Tuesday, but finished their matches. Canadian qualifier Frank Dancevic said he blacked out during his 7-6 (12), 6-3, 6-4 loss to No. 27-seeded Benoit Paire of France.
Dancevic, who required medical attention during the second set, questioned the wisdom of not suspending matches during the torridly hot conditions.
''I don't think it's fair to anybody, to the players, to the fans, to the sport when you see players pulling out of matches and passing out,'' he said. ''''I think it's definitely hazardous to be out there. It's dangerous.''
On the women's side, Polona Hercog of Slovenia retired with a shoulder injury after losing the first game of her match against 25th-seeded Alize Cornet of France.
Hercog, who was only on court for 10 minutes, collected 30,000 Australian dollars ($27,000) for losing in the first round, or AU$3,000 ($2,700) per minute.
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