For the fifth consecutive season in the Stanley Cup Final, the Eastern Conference participant holds a 2-1 series lead.
In the last three years, the Eastern Conference champion has gone on to hoist the Stanley Cup, with the Tampa Bay Lightning in 2015 being the only team to blow that advantage.
The last time the Bruins were in the Stanley Cup Final, they took a 2-1 lead into Game 4, but they could not hold on to beat the Chicago Blackhawks in 2013.
Although they face an uphill climb in the series, the St. Louis Blues are in a familiar situation, as they rallied from down 2-1 to beat the San Jose Sharks to win the Western Conference Final.
Stanley Cup Final Schedule
All times Eastern.
Game 4: Monday, June 3, at St. Louis (8 p.m., NBC)
Game 5: Thursday, June 6, at Boston (8 p.m., NBC)
Game 6: Sunday, June 9, at St. Louis (8 p.m., NBC)*
Game 7: Wednesday, June 12, at Boston (8 p.m., NBC)*
Updated Stanley Cup Final Odds
Odds via Oddschecker.
To Win Series
Boston (-310; bet $310 to win $100)
St. Louis (+245; bet $100 to win $245)
Boston appears to be in great shape after posting seven goals in Game 3 at Enterprise Center to earn its fifth straight postseason road win.
Since losing Game 3 of their second-round series with the Columbus Blue Jackets, the Bruins are 9-1 across three series.
The only loss during that stretch was suffered at home in overtime in Game 2 of the Stanley Cup Final.
In most situations, the Bruins would be seen as the overwhelming favorite, but the Blues reversed a similar lead after a more deflating Game 3 loss to San Jose in the last round.
The Blues fell in overtime in Game 3 of the Western Conference Final on a controversial hand pass by San Jose's Timo Meier that led to the game-winning goal.
But instead of letting that result deflate them, the Blues bounced back with a Game 4 victory that spurred a three-game winning run to clinch a spot in the Stanley Cup Final.
Of course, the Blues have to take things game-by-game at the moment, but if you look at the series from a wider perspective, they are going to have to hold serve at home and win once more on the road to earn the franchise's first Stanley Cup.
It is a tough spot to be in, but the Blues have plenty of experience grinding out series victories, as all three of their postseason matchups have gone to at least six games.
However, the Bruins are different from any of the three teams the Blues have faced during their postseason run.
Boston is receiving contributions from all parts of its lineup, with Torey Krug emerging as the latest star in Game 3 with one goal and three assists.
Goalie Tuukka Rask is also playing well with seven goals against in three games, and in Game 3, he tied Gerry Cheevers for the most road wins by a goalie in Bruins postseason history, per NHL Public Relations:
In addition to outscoring the Blues 13-6, the Bruins have had five more players find the back of the net than their Western Conference foe.
Boston has had 11 different scorers over three games, with Sean Kuraly and Charlie Coyle being the only multiple-goal scorers.
The Bruins also carry an advantage in special teams with six power-play goals compared to one from St. Louis, with four of those coming in Game 3.
Even though St. Louis has proved it is capable of pulling itself out of a hole in the playoffs, Boston has scoring depth and goalie play going in its favor right now.
Until the Blues prove they can defend their home ice, the Bruins have to be the pick to win the series, even if they will not produce a large payout at this point.
If you have trust St. Louis will reverse its form in Game 4, it is worth making a small bet on the team to win the series now before the value decreases.
Follow Joe on Twitter, @JTansey90.
Statistics obtained from Hockey Reference.