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  With the score 1-1, victory on Saturday would mean Andy Murray could win the best-of-five tie for Great Britain in Sunday's first reverse singles.
  Jamie Murray and Dom Inglot were originally named to face Lleyton Hewitt and Sam Groth.
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  But captain Leon Smith exercised his right to change the line-up.
  "Everyone in the team wants to play, everyone wants to try and help where they can," Andy Murray said on Friday.
  Jamie Murray has reached the last two Grand Slam finals, at Wimbledon and the US Open, with Australian partner John Peers, while Inglot reached the semi-finals in New York with Sweden's Robert Lindstedt.
  Britain captain Leon Smith had said he would not decide on his line-up until after Friday's play, saying he needed to "talk to Andy", but he has now opted for the pairing who secured a four-set victory over Nicolas Mahut and Jo-Wilfried Tsonga in the quarter-final against France.
  Murray, the world number three, thrashed Thanasi Kokkinakis 6-3 6-0 6-3 in Friday's first singles match against Australia, before Bernard Tomic beat Dan Evans 6-3 7-6 (7-2) 6-7 (5-7) 6-4.
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  Australia captain Wally Masur admitted his side were feeling the pressure ahead of the crucial third rubber.
  "The locker room is pretty tense because I guess we thought it would be 1-1 and it's come to that situation, where there's so much focus on the doubles," he said.
  "Everybody knows how pivotal that match will be but we're very happy to be in it."
summary: Andy Murray will team up with his brother Jamie for Saturday's crucial doubles match against Australia in the Davis Cup semi-final.