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Australia face a major dilemma about how to balance their line-up in the absence of injured all-rounder Shane Watson without disrupting their winning momentum.
The reigning world champions have won all five of their matches in the tournament as they attempt to become the first side in history to claim three successive World Cups.
But the loss of 25-year-old Watson, who tore his left calf muscle against Bangladesh earlier this week and could be out for up to three weeks, looks certain to upset their balance for their forthcoming matches.
"Losing an all-rounder out of your side does change things around quite a bit," admitted captain Ricky Ponting.
"If he's going to miss the next game we will have to really think about what the best line-up is going to be. He's been playing as our fourth quick, [and] happens to be pretty handy with the bat."
Australia are most likely to replace Watson with Brad Hodge, who will strengthen the batting order and can also contribute some off-spin, but his inclusion will weaken their bowling options.
The other possibility is to play an extra bowler and include Stuart Clark or left-arm seamer Mitchell Johnson, but that would weaken their batting options.
Watson will certainly miss Sunday's match against England, which gives Australia a chance to avenge their shock Commonwealth Bank Series defeat, but he is expected to fit for either of the semi-finals on April 24 and 25.
"I want to review it later in the week. It all depends on how quickly he's improving," said Australia physiotherapist Alex Kontouris.
"If he is feeling great by the end of the week, the prognosis is very good. If it's not, it's probably going to take a lot longer to recover."
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