"Ireland is dark horse in ICC World Cup 2015"
"Nepal is dark horse among associate nation"
Above lines show that dark horse means ability to defeat the strong team with surprisingly . Some sort of different result is expected in the exercise and then we can use the word like "Dark Horse". As we know that dark horse team seems strong enough in ccomparison to other horses.
In a daily life when a person does his deed in a different way also seems to be a dark horse but there should be competition between different parties, then one of the competent may be dark horse.
