The Warriors were -150 favorites to capture the championship as of Thursday morning and have attracted the majority of bets to win the best-of-seven series at most sportsbooks. At online sportsbook PointsBet, 87% of the money has been wagered on the Warriors to win the Finals.
The largest reported bets, however, have been on the Celtics, including a couple from bettors whose opinions are respected by bookmakers.
Jeff Sherman, a vice president of risk who oversees NBA odds for the SuperBook in Las Vegas, told ESPN that his shop accepted multiple bets on the Celtics to win the series at odds of +145 and +140 from influential bettors as well as a money-line bet on Boston to win Game 1 on Thursday in San Francisco.
"I really respect the two [bettors] that played the sharp stuff with us on the Game 1 money line and the series," Sherman told ESPN in a text message.
In addition, Caesars Sportsbook reported taking a $100,000 bet on the Celtics to win the series at +140 odds. It's the largest wager the book had taken as of Wednesday.
Even with the big bet on Boston, Craig Mucklow, Caesars' head of trading, said the book needs the underdog Celtics in the series and in Game 1.
Golden State is a consensus 3.5-point favorite in the series opener. As of Wednesday afternoon, 80% of the spread bets at FanDuel were on the Warriors.
Boston has been overlooked by the betting public from the start, though. The Celtics entered the season as 50-1 long shots to win the championship and received little interest from bettors. At PointsBet, there were more bets -- and more money wagered -- on the Detroit Pistons to win the NBA title than there were on the Celtics as the season tipped off in October.
Based on the preseason odds, if the Celtics win the title, they would become the biggest long-shot champion in the past 35 seasons, according to sports-betting database SportsOddsHistory.com.