CARLTON has suffered a double blow ahead of the NAB Challenge with defender Andrew Walker forced to undergo more surgery on his troublesome knee and skipper Marc Murphy ruled out for the next three weeks with a calf strain.

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Murphy strained his calf in the Blues' intra-club game last Friday and has been ruled out of their opening NAB Challenge campaign game West Coast in Mandurah on Friday night. 
But Carlton is hopeful the midfielder will be fit to play in its remaining two pre-season games against Collingwood in Bendigo on March 15 and Geelong at Etihad Stadium on March 22. 
However, Walker looks set to play no part in those pre-season games after recently undergoing his third bout of surgery on the same knee since July last year.
Nonetheless, Carlton football manager Andrew McKay said Walker remained some chance of playing in the Blues' round one clash against Richmond on April 2.
"It's unfortunate that Andrew's had another setback with his knee, however we are looking forward to him returning to full training soon and he remains in contention for round one," McKay said on Tuesday.
"Andrew was progressing well in his recovery, but last week pinched his meniscus while training.
"We're confident this procedure will have him back to his best and he will play an important role for us this year."
Murphy experienced calf tightness during the Blues intra-club match, with scans later revealing he had suffered a calf strain that was expected to sideline him for two to three weeks.
"Although this is unfortunate, Marc will still be able to take part in the final two NAB Challenge games to enable him to be fully fit for round one against Richmond," McKay said.
Walker had knee surgery in July last year after managing lingering soreness for much of 2014's first 17 rounds, then had further surgery before Christmas when his rehabilitation program stalled.
Walker had hoped to play in the Blues' final NAB Challenge game when he spoke to last week, but his latest setback means he will enter the 2015 season on a severely limited preparation.

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