If you never knew, the cock fighting is equally a luck base game, as in most cases is not always the biggest cock who wins a fight, just as in our normal MMA fighting, which requires skills, basic experience and more exposure to other cock for fighting will determine if a cock might either win or lose a fight during the main gambling fight.
That's what you called
"upset" since if by luck, an underdog cock can land its
"tari" (a metal pointed blade attached to a fighting cock's legs) into an opening spot and that means a sure Knock Out already. However, you can't rely on that most of the time that's why it's still better to refer to the fighting cocks' record and stats. It was an effective strategy most of the time although expect low odds for favorites
(sometimes between 1.7 to 1.8 depending on the number of bettors on that round).
However, there are some flaws in this game too especially in manipulating the result. One way is thru the involvement of what we called here as
"saltador" (the one that acts as a referee) where during the verdict stage, he might possibly give the other cock additional injury to somehow weakened and lose that match. There are lots of professional
"saltador" here where even in front of the camera, they can hide their tricks.
Note: The terms I used here and a bit of shared gameplay are based on our country's way of doing cockfighting. I'm not sure how cockfighting is being played in other countries.