The phrase "huge underdogs" means that someone or a team is not expected to win because their opponent is much stronger or more likely to succeed. Full definition
I'm just one person, but I pledge to do my part in embracing other cultures by betting on far - away countries as huge underdogs in the Winter Olympics and World Cup. (sportsinsights.com)
The Russians will not be huge underdogs in the tie, but with us being able to concentrate on the competition we should put them to the sword tonight. (justarsenal.com)
These guys came into this game huge underdogs but fought every second and battled the entire game. (allsportsseries.com)