As a coach, you have to sell that to your players even at times if you dont believe it. Especially if it is one of the few games you can be competitive in. Upsets dont happen without belief.
It is very hard to get a team that is getting beat down continiously to believe late in the year, even when it is a game they can compete in, because the weight of the season has caused them to give up easy. It is a very hard coaching situation.
getting a team who has been getting killed to still play hard is a tough thing to do.