Cahill was supposed to be sidelined for up to three weeks but Petke is of the belief that he may be able to play some sort of role at the RFK Stadium on Saturday.
"There's always reason for optimism with Tim," Petketold reporters.
"But I think with only two more sessions to go before the game, if I was a betting man, if anything, he'll be used in a role off the bench or something along that aspect at this point."
The former Everton star missed Red Bulls training on Wednesday but that hasn't stopped Petke from using an optimistic outlook regarding his fitness as he targets a season-first win for his side.
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