dark horse

(noun) a competitor that has little to no chance of winning

Example Sentence:

Canada is the dark horse in tonight’s football match, because they are playing Brazil.

Media:

Similar idioms:

1. underdog
2. take a stab in the dark
3. on one’s high horse
4. look a gift horse in the mouth
5. so hungry one could eat a horse
6. jump at the chance
7. birds of a feather, flock together
8. out of the question