Andy Murray withdrew from the Brisbane International, citing ongoing problems with his right hip, hours after women's top seed Garbine Muguruza retired in the third set of her opening match because of leg cramps.
Former No. 1-ranked Murray was scheduled to play Thursday in his return to competitive tennis for the first time since July but notified organizers he was pulling out after failing to practice on Tuesday.
''I came here with every intention of making a strong start to the year, but sadly my team and I don't feel that I'm where I need to be just yet to compete at the highest level,'' said Murray, who has won the title here twice.
Muguruza fell to the court behind the baseline before retiring from her opening match while leading in the third set against Aleksandra Krunic.
The Wimbledon champion had been up a set and a break but couldn't close it out in straight sets as Krunic rallied from 5-2 down in the second, winning it in a tiebreaker to force the match into a third set.
Muguruza, who held the No. 1 ranking for four weeks last year, was stopped by the cramps after almost 2 1/2 hours in humid conditions on Pat Rafter Arena, giving Krunic a 5-7, 7-6 (3), 1-2 retired, victory.
''I don't really cramp a lot, so I'm actually surprised that today my body was like that,'' Muguruza said, adding that her calf muscles started to cramp early in the second set. ''It's a shame because I always come here excited about the first tournament, and this one was bad luck, I guess.''
Krunic advanced to a quarterfinal match against seventh-seeded Anastasija Sevastova, who beat Sorana Cirstea 6-2, 6-1.
''It's definitely not a nice feeling, first of all for me as an athlete, to see my colleague walking out of the court not being able to finish the match,'' Krunic said in an on-court TV interview. ''I want to wish Garbine a fast recovery and I hope she gets better for the Slam.''
Alize Cornet reached the quarterfinals with a 6-1, 7-5 win over Mirjana Lucic-Baroni.
The Brisbane International had been Muguruza's only scheduled tuneup event before the Australian Open, the first major of the season starting Jan. 15.
''I'm going to evaluate what options do I have now ... maybe just go right away to Melbourne,'' Muguruza said. ''I didn't expect to not continue here.''
The 30-year-old Murray planned to remain in Brisbane preparing for the season's first major, where he's aiming to return to tournament play for the first time since a quarterfinal exit at Wimbledon.
Murray has been a five-time runner-up at the Australian Open, but never won the title. He entered last season with the No. 1-ranking but was knocked out in the fourth round - his earliest exit in eight years at Melbourne Park. While being sidelined with the hip problem, Murray's ranking slipped to a year-end No. 16.
He's not the only leading player trying to overcome injury, with top-ranked Rafael Nadal and Novak Djokovic also trying to recover in time for the Australian Open.
In men's first-round matches in Brisbane, U.S. qualifier Michael Mmoh beat Federico Delbonis 6-3, 6-4, Chung Hyeon upset fifth-seeded Gilles Muller 6-3, 7-6 (1), Kyle Edmund rallied for a 6-7 (5), 7-6 (4), 6-4 win over Denis Shapovalov and Denis Istomin beat No. 7-seeded Damir Dzumhur 6-7 (4), 6-3, 6-2.
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