The Fire take on the MLS Cup winners at the StubHub Center on Friday, March 6 but may be without off-season Designated Player signing Accam.
The Ghanaian striker sustained a groin strain in a pre-season friendly against Norwegian side Stabaek on the weekend and is now in doubt for the opening weekend's fixture.
"He's got a slight strain, and the first five days determine how bad it is," said Fire head coach Frank Yallop told.
"We're on day two or three of it right now, so we'll know more in a couple of days to see what the extent of it is. He's had an MRI, there's a slight something there, and if he's a quick healer, which hopefully he is, he could be available for the [season opener].
"But there's no chance we're going to risk him just for one match."
Of the former Helsingborg ace, Yallop added: "We want to make sure he's ready to go and firing on all cylinders when he does get back.
"He's back in Chicago right now, getting treatment three times a day, and we're just trying to get him ready as quick as we can."
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