What is Underdog in Sports Betting?

Underdog Explained in Detail

The underdog is the opposite of the favorite. In every game with a clear expected outcome, one side is favored and the other is the underdog. The sportsbook expresses this through the odds: the underdog gets positive moneyline odds and receives points on the spread. In a pick'em game where both teams are considered equal, there is no underdog.

Underdog betting is popular among professional bettors for several reasons. First, the public tends to overbet favorites, which can inflate the odds on underdogs. Second, the emotional satisfaction of backing a winner who is expected to lose creates a psychological barrier for recreational bettors, leaving more value on the table for those willing to take the other side.

The value of an underdog bet is not determined by whether the team wins but by whether the odds accurately reflect the true probability. A +200 underdog who truly has a 40% chance of winning is a fantastic bet even though they will lose more often than they win. Over time, the higher payout on wins more than compensates for the more frequent losses.

Underdogs have historically performed well against the spread in several situations: home underdogs in the NFL, large underdogs in conference games where familiarity breeds competitive games, and underdogs following a bye week. These situational angles are starting points for deeper analysis, not standalone betting systems.