small chance

also-ran long shot sleeper underdog

hundred-to-one shot improbability little chance little opportunity outside chance outside shot poor bet poor lookout poor possibility poor prognosis poor prospect slim chance stalking horse unexpected winner unknown unknown quantity unlikelihood unlikely winner upsetter

chance in a million ghost of a chance impossible no chance no way not a prayer poor outlook poor possibility poor prospect slim chance snowball's chance in hell unthinkable very little chance when hell freezes over

fluke

chance hit hundred-to-one shot little chance long odds lucky shot no chance off-chance one in a million outside chance poor bed slim chance