Del Potro, Safina out, Nadal, Murray to meet

---

Justine Henin of Belgium celebrates match point in her victory over Yanina Wickmayer of Belgium in their women's singles fourth round match on day seven of the Australian Open tennis tournament in Melbourne Sunday. Henin continued her amazing comeback whe

MELBOURNE, Australia, Jan 24 (AP): US Open champion Juan Martin del Potro's bid for back-to-back Grand Slam titles ended in a fourth-round, five-set loss to No. 14 Marin Cilic Sunday.
Two higher-ranked women's seeds, both Russian, made their exits with him.
Second-ranked Dinara Safina retired while she was down 4-5, serving at 30-40 in the first set against Maria Kirilenko, who had ousted 2008 champion and fellow Russian Maria Sharapova in the first round.
No. 3 Svetlana Kuzne-tsova lost 6-3, 3-6, 6-1 to Nadia Petrova, who went into the match after a stunning, 6-0, 6-1 third-round victory over US Open champion Kim Clijsters.
While the seeded players dropped, former No. 1 Justine Henin continued her run in her first Grand Slam tournament in two years with a 7-6 (3), 1-6, 6-3 win over fellow Belgian Yanina Wickmayer, keeping her on track for a quarterfinal meeting with Petrova.
"Today was similar. I felt like my motivation, my concentration was on the same level," said Petrova, comparing her wins over Clijsters and French Open champion Kuznetsova. The 27-year-old Russian doesn't think she's reached her potential yet-her best runs in the majors finishing in semifinal losses.
"I know there's still a lot to accomplish," Petrova said. "That's what I'm really looking for."
Safina, the 2009 Australian finalist who held the No. 1 ranking despite never winning a major, limped off when facing set point against Kirilenko when a back problem flared up.
Defending champion Nadal and Andy Murray held off two of the tallest men and biggest servers in tennis earlier on Rod Laver Arena to set up a quarterfinal meeting.
Nadal, who beat Federer in the 2009 final, had a 6-4, 4-6, 6-4, 6-4 win over 2.08 (6-foot-10) Ivo Karlovic of Croatia, the tallest man on the tour.
No. 5 Murray overcame 2.06-metre (6-foot-9) American John Isner 7-6 (4), 6-3, 6-2 to reach the final eight in Australia for the first time. The 22-year-old Scot hasn't dropped a set in four matches.
In an afternoon match at Hisense, 2008 Wimbledon semifinalist Zheng Jie set another national mark by becoming the first Chinese player to reach the quarterfinals at Melbourne Park with a 7-6 (6), 6-4 victory over Alona Bondarenko. She next plays Kirilenko.